This adds a few tiny fixes for les and the p2p simulation framework:

LES Parts

- Keep the LES-SERVER connection even it's non-synced

  We had this idea to reject the connections in LES protocol if the les-server itself is
  not synced. However, in LES protocol we will also receive the connection from another
  les-server. In this case even the local node is not synced yet, we should keep the tcp
  connection for other protocols(e.g. eth protocol).

- Don't count "invalid message" for non-existing GetBlockHeadersMsg request

  In the eth syncing mechanism (full sync, fast sync, light sync), it will try to fetch
  some non-existent blocks or headers(to ensure we indeed download all the missing chain).
  In this case, it's possible that the les-server will receive the request for
  non-existent headers. So don't count it as the "invalid message" for scheduling
  dropping.

- Copy the announce object in the closure

  Before the les-server pushes the latest headers to all connected clients, it will create
  a closure and queue it in the underlying request scheduler. In some scenarios it's
  problematic. E.g, in private networks, the block can be mined very fast. So before the
  first closure is executed, we may already update the latest_announce object. So actually
  the "announce" object we want to send is replaced.

  The downsize is the client will receive two announces with the same td and then drop the
  server.

P2P Simulation Framework

- Don't double register the protocol services in p2p-simulation "Start".

  The protocols upon the devp2p are registered in the "New node stage". So don't reigster
  them again when starting a node in the p2p simulation framework

- Add one more new config field "ExternalSigner", in order to use clef service in the
  framework.

* core/state/snapshot: introduce snapshot journal version

* core: update the disk layer in an atomic way

* core: persist the disk layer generator periodically

* core/state/snapshot: improve logging

* core/state/snapshot: forcibly ensure the legacy snapshot is matched

* core/state/snapshot: add debug logs

* core, tests: fix tests and special recovery case

* core: polish

* core: add more blockchain tests for snapshot recovery

* core/state: fix comment

* core: add recovery flag for snapshot

* core: add restart after start-after-crash tests

* core/rawdb: fix imports

* core: fix tests

* core: remove log

* core/state/snapshot: fix snapshot

* core: avoid callbacks in SetHead

* core: fix setHead cornercase where the threshold root has state

* core: small docs for the test cases

Co-authored-by: Péter Szilágyi <peterke@gmail.com>

* core/state/snapshot: add diskRoot function

* core/state/snapshot: disable iteration if the snapshot is generating

* core/state/snapshot: simplify the function

* core/state: panic for undefined layer

* core/state: maintain one more diff layer

* core/state: address comment

* accounts/abi/bind: restore error functionality

* Update accounts/abi/bind/base.go

Co-authored-by: Guillaume Ballet <gballet@gmail.com>

Co-authored-by: Guillaume Ballet <gballet@gmail.com>

params: update yolov2 bootnode with elastic ip

utils, params: add yolov2 bootnode

The old one was wrong in two ways: the first block in chain.rlp was the
genesis block, and the genesis difficulty was below minimum difficulty.

This also contains some other fixes to the test.

* core/vm, core/state: implement EIP-2929 + YOLOv2

* core/state, core/vm: fix some review concerns

* core/state, core/vm: address review concerns

* core/vm: address review concerns

* core/vm: better documentation

* core/vm: unify sload cost as fully dynamic

* core/vm: fix typo

* core/vm/runtime: fix compilation flaw

* core/vm/runtime: fix renaming-err leftovers

* core/vm: renaming

* params/config: use correct yolov2 chainid for config

* core, params: use a proper new genesis for yolov2

* core/state/tests: golinter nitpicks

The version check logic did not take into account the second digit (i.e. the '4' in v1.4.0) - this one line patch corrects this.

* les: move NodeStateMachine from clientPool to LesServer

* les: new header broadcaster

* les: peerCommons.headInfo always contains last announced head

* les: remove clientPeerSet and serverSet

* les: fixed panic

* les: fixed --nodiscover option

* les: disconnect all peers at ns.Stop()

* les: added comments and fixed signed broadcasts

* les: removed unused parameter, fixed tests

* Fix potential nil pointer error when neither block number nor hash is specified to accountRange

* Update error description

* core: add background indexer to waitgroup

* core: make indexer stopable

* core/rawdb: add unit tests

* core/rawdb: fix lint

* core/rawdb: fix tests

* core/rawdb: fix linter

* add interrupt counter

* remove interrupt counter, allow ctrl-C to clear ONLY, ctrl-D will terminate console, stop node

* format

* add instructions to exit

* fix tests

* core/vm: marshall returnData as hexstring in trace logs

* core/vm: marshall returnData as hexstring in trace logs

This change implements the Discovery v5.1 wire protocol and
also adds an interactive test suite for this protocol.

* accounts/keystore: add timeout to test to prevent failure on travis

The TestWalletNotifications test sporadically fails on travis.
This is because we shutdown the event collection before all events are received.
Adding a small timeout (10 milliseconds) allows the collector to be scheduled
and to consume all pending events before we shut it down.

* accounts/keystore: added newlines back in

* accounts/keystore: properly fix the walletNotifications test

* miner: exit loop when downloader Done or Failed

Following the logic of the comment at the method,
this fixes a regression introduced at 7cf56d6f
, which would allow external parties to DoS with
blocks, preventing mining progress.

Signed-off-by: meows <b5c6@protonmail.com>

* miner: remove ineff assign (lint)

Signed-off-by: meows <b5c6@protonmail.com>

* miner: update test re downloader events

Signed-off-by: meows <b5c6@protonmail.com>

* Revert "miner: remove ineff assign (lint)"

This reverts commit eaefcd34ab4862ebc936fb8a07578aa2744bc058.

* Revert "miner: exit loop when downloader Done or Failed"

This reverts commit 23abd34265aa246c38fc390bb72572ad6ae9fe3b.

* miner: add test showing imprecise TestMiner

Signed-off-by: meows <b5c6@protonmail.com>

* miner: fix waitForMiningState precision

This helper function would return an affirmation
on the first positive match on a desired bool.

This was imprecise; it return false positives
by not waiting initially for an 'updated' value.

This fix causes TestMiner_2 to fail, which is
expected.

Signed-off-by: meows <b5c6@protonmail.com>

* miner: remove TestMiner_2 demonstrating broken test

This test demonstrated the imprecision of the test
helper function waitForMiningState. This function
has been fixed with 6d365c2851, and this test test
may now be removed.

Signed-off-by: meows <b5c6@protonmail.com>

* miner: fix test regarding downloader event/mining expectations

See comment for logic.

Signed-off-by: meows <b5c6@protonmail.com>

* miner: add test describing expectations for downloader/mining events

We expect that once the downloader emits a DoneEvent,
signaling a successful sync, that subsequent StartEvents
are not longer permitted to stop the miner.

This prevents a security vulnerability where forced syncs via
fake high blocks would stall mining operation.

Signed-off-by: meows <b5c6@protonmail.com>

* miner: use 'canStop' state to fix downloader event handling

- Break downloader event handling into event
separating Done and Failed events. We need to
treat these cases differently since a DoneEvent
should prevent the miner from being stopped on
subsequent downloader Start events.

- Use canStop state to handle the one-off
case when a downloader first succeeds.

Signed-off-by: meows <b5c6@protonmail.com>

* miner: improve comment wording

Signed-off-by: meows <b5c6@protonmail.com>

* miner: start mining on downloader events iff not already mining

Signed-off-by: meows <b5c6@protonmail.com>

* miner: refactor miner update logic w/r/t downloader events

This makes mining pause/start logic regarding downloader
events more explicit. Instead of eternally handling downloader
events after the first done event, the subscription is closed
when downloader events are no longer actionable.

Signed-off-by: meows <b5c6@protonmail.com>

* miner: fix handling downloader events on subcription closed

Signed-off-by: meows <b5c6@protonmail.com>

* miner: (lint:gosimple) use range over chan instead of for/select

Signed-off-by: meows <b5c6@protonmail.com>

* miner: refactor update loop to remove race condition

The go routine handling the downloader events handling
vars in parallel with the parent routine, causing a
race condition.

This change, though ugly, remove the condition while
still allowing the downloader event subscription to be
closed when the miner has no further use for it (ie DoneEvent).

* miner: alternate fix for miner-flaw

Co-authored-by: meows <b5c6@protonmail.com>

* peer: return localAddr instead of name to prevent spam

We currently use the name (which can be freely set by the peer) in several log messages.
This enables malicious actors to write spam into your geth log.
This commit returns the localAddr instead of the freely settable name.

* p2p: reduce usage of peer.Name in warn messages

* eth, p2p: use truncated names

* Update peer.go

Co-authored-by: Marius van der Wijden <m.vanderwijden@live.de>
Co-authored-by: Felix Lange <fjl@twurst.com>

* imporve some web3-ext apis

* Update web3ext.go

Co-authored-by: Felix Lange <fjl@twurst.com>

* trie: polish commit function

* trie: fix typo

* eth/downloader: fix data race around the ancientlimit

* eth/downloader: initialize the ancientlimit as 0

* core/vm: dedup config check

* review feedback: reuse buffer