This commit makes various cleanup changes to rlp.Stream.

* rlp: shrink Stream struct

This removes a lot of unused padding space in Stream by reordering the
fields. The size of Stream changes from 120 bytes to 88 bytes. Stream
instances are internally cached and reused using sync.Pool, so this does
not improve performance.

* rlp: simplify list stack

The list stack kept track of the size of the current list context as
well as the current offset into it. The size had to be stored in the
stack in order to subtract it from the remaining bytes of any enclosing
list in ListEnd. It seems that this can be implemented in a simpler
way: just subtract the size from the enclosing list context in List instead.

This changes the definitions of Ping and Pong, adding an optional field
for the sequence number. This field was previously encoded/decoded using
the "tail" struct tag, but using "optional" is much nicer.

* forkid: added failing test

* forkid: fixed off-by-one bug

This PR fixes two errors that regressed when EIP-1559 was merged.

This is the initial implementation of EIP-1559 in packages core/types and core.
Mining, RPC, etc. will be added in subsequent commits.

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

* cmd/evm: return json error if unmarshalling from stdin fails

* cmd/evm: make error capitalizations uniform (all lowercase starts)

* cmd/evm: capitalize error sent directly to stderror

* cmd/geth, eth, core: snapshot dump + unify with trie dump

* cmd/evm: dump API fixes

* cmd/geth, core, eth: fix some remaining errors

* cmd/evm: dump - add limit, support address startkey, address review concerns

* cmd, core/state, eth: minor polishes, fix snap dump crash, unify format

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

consensus/ethash: implement EIP-3554 (bomb delay)

* Ensure state could be created in ToBlock

* Fix rebase errors

* use a panic instead

eth/tracers: do the JSON serialization via .js to capture C faults

This adds a cmd line parameter `--gpo.ignoreprice`, to make the gas price oracle ignore transactions below the given threshold.

* core/types: remove support for legacy receipt storage encoding

* core/types: remove support for legacy log storage encoding

Getting the raw value is not necessary to decode this type, and
decoding it directly from the stream is faster.

'geth monitor' subcommand is no longer supported.

This adds support for a new struct tag "optional". Using this tag, structs used
for RLP encoding/decoding can be extended in a backwards-compatible way,
by adding new fields at the end.

* core, params: implement EIP-3529

* core/vm: add london instructionset

* core/vm: add method doc for EIP enabler

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

core: implement EIP-3541

* all: define London+baikal, undefine yolov3, add london override flag

* cmd, core, params: add baikal genesis definition

This changes the SimultaneousRequests test to send the requests from the same
connection, as it doesn't really make sense to test whether a node can respond
to two requests with different request IDs from separate connections.

With the update to a newer AppVeyor build image, creating the Windows
installer no longer worked because of a string quoting error in EnvVarUpdate.nsh.

This applies the fix recommended in https://stackoverflow.com/questions/62081765.

This fixes a regression introduced in #22804.

This updates go.mod for the addition of golang.org/x/sync.

This PR cleans up the CI build system and fixes a couple of issues.

- The go tool launcher code has been moved to internal/build. With the new
  toolchain functions, the environment of the host Go (i.e. the one that built
  ci.go) and the target Go (i.e. the toolchain downloaded by -dlgo) are isolated
  more strictly. This is important to make cross compilation and -dlgo work
  correctly in more cases.
- The -dlgo option now skips the download and uses the host Go if the running Go
  version matches dlgoVersion exactly.
- The 'test' command now supports -dlgo, -cc and -arch. Running unit tests with
  foreign GOARCH is occasionally useful. For example, it can be used to run
  32-bit tests on Windows. It can also be used to run darwin/amd64 tests on
  darwin/arm64 using Rosetta 2.
- The 'aar', 'xcode' and 'xgo' commands now use a slightly different method to
  install external tools. They previously used `go get`, but this comes with the
  annoying side effect of modifying go.mod. They now use `go install` instead,
  which is the recommended way of installing tools without modifying the local
  module.
- The old build warning about outdated Go version has been removed because we're
  much better at keeping backwards compatibility now.

This removes auto-configuration of the snap.*.ethdisco.net DNS discovery tree.
Since measurements have shown that > 75% of nodes in all.*.ethdisco.net support
snap, we have decided to retire the dedicated index for snap and just use the eth
tree instead.

The dial iterators of eth and snap now use the same DNS tree in the default configuration,
so both iterators should use the same DNS discovery client instance. This ensures that
the record cache and rate limit are shared. Records will not be requested multiple times.

While testing the change, I noticed that duplicate DNS requests do happen even
when the client instance is shared. This is because the two iterators request the tree
root, link tree root, and first levels of the tree in lockstep. To avoid this problem, the
change also adds a singleflight.Group instance in the client. When one iterator
attempts to resolve an entry which is already being resolved, the singleflight object
waits for the existing resolve call to finish and returns the entry to both places.

eth: don't print db upgrade warning on db init