This reverts commit 460d206f.

* swarm/shed, swarm/storage/localstore: add LastPullSubscriptionChunk

* swarm/shed: fix comments

* swarm/shed: fix TestIncByteSlice test

* swarm/storage/localstore: fix TestDB_LastPullSubscriptionChunk

build/deb: fix PPA env var setting

build/deb: use custom cache for PPA builder

crypto/bn256/cloudflare: pull in upstream fix for Go 1.12 R18

core/types: fix receipt legacy decoding

* p2p/discover: remove unused function

* p2p/enode: use localItemKey for local sequence number

I added localItemKey for this purpose in #18963, but then
forgot to actually use it. This changes the database layout
yet again and requires bumping the version number.

* node: require LocalAppData variable

This avoids path inconsistencies on Windows XP.
Hat tip to @MicahZoltu for catching this so quickly.

* node: fix typo

* swarm/network: WIP consider all nodes for healthy iteration

* swarm/network/simulation: extend TestWaitTillHealthy to really check kads are healthy

* cmd/swarm/swarm-snapshot: fixed bugs in snapshot creation binary

* swarm/network/simulation: addressed PR comments

* swarm/network/simulation: defer sim.Clsoe()

* swarm/network/simulation: fixed wrong sim.Close()

* swarm/network/simulation: addressed PR comments

* cmd/swarm/swarm-snapshot: reducing default to 8 nodes, more to 4

* cmd/swarm/swarm-snapshot: extended timeout to 3 mins, or 256 nodes snapshot times out

* swarm/network/simulation: More PR comments

Upgrade to Go 1.12

* travis, build: switch to NDK 19b, fix gomobile builds

* travis, build: move NDK into its final bundle location

* travis: disable Android build on PRs once again

containers/docker: nuke per the 1.8.0 deprecation note

This change

- implements concurrent LES request serving even for a single peer.
- replaces the request cost estimation method with a cost table based on
  benchmarks which gives much more consistent results. Until now the
  allowed number of light peers was just a guess which probably contributed
  a lot to the fluctuating quality of available service. Everything related
  to request cost is implemented in a single object, the 'cost tracker'. It
  uses a fixed cost table with a global 'correction factor'. Benchmark code
  is included and can be run at any time to adapt costs to low-level
  implementation changes.
- reimplements flowcontrol.ClientManager in a cleaner and more efficient
  way, with added capabilities: There is now control over bandwidth, which
  allows using the flow control parameters for client prioritization.
  Target utilization over 100 percent is now supported to model concurrent
  request processing. Total serving bandwidth is reduced during block
  processing to prevent database contention.
- implements an RPC API for the LES servers allowing server operators to
  assign priority bandwidth to certain clients and change prioritized
  status even while the client is connected. The new API is meant for
  cases where server operators charge for LES using an off-protocol mechanism.
- adds a unit test for the new client manager.
- adds an end-to-end test using the network simulator that tests bandwidth
  control functions through the new API.

build: bump PPA builders to Go 1.11

* swarm/pss: fix data race on HandshakeController.symKeyIndex

The HandshakeController.symKeyIndex map was accessed concurrently.
Since insufficient test coverage the race is not detected every time.
However, running TestClientHandshake a 100 times seems to be enough to
reproduce the race.

Note: I've chosen HandshakeController.lock to protect
HandshakeController.symKeyIndex as that was already protected in a few
functions by that lock.

Additionally:
- removed unused testStore
- enabled tests in handshake_test.go as they pass
- removed code duplication by adding getSymKey()

* swarm/pss: fix a data race on HandshakeController.keyC

* swarm/pss: fix data races with on Pss.symKeyPool

Prevents reallocation, improves performance

* swarm/storage/mock: implement listings methods for mem and rpc stores

* swarm/storage/mock/rpc: add comments and newTestStore helper function

* swarm/storage/mock/mem: add missing comments

* swarm/storage/mock: add comments to new types and constants

* swarm/storage/mock/db: implement listings for mock/db global store

* swarm/storage/mock/test: add comments for MockStoreListings

* swarm/storage/mock/explorer: initial implementation

* cmd/swarm/global-store: add chunk explorer

* cmd/swarm/global-store: add chunk explorer tests

* swarm/storage/mock/explorer: add tests

* swarm/storage/mock/explorer: add swagger api definition

* swarm/storage/mock/explorer: not-zero test values for invalid addr and key

* swarm/storage/mock/explorer: test wildcard cors origin

* swarm/storage/mock/db: renames based on Fabio's suggestions

* swarm/storage/mock/explorer: add more comments to testHandler function

* cmd/swarm/global-store: terminate subprocess with Kill in tests

* swarm/storage/localstore: close localstore in two tests

* swarm/storage/localstore: fix a possible deadlock in tests

* swarm/storage/localstore: re-enable pull subs tests for travis race

* swarm/storage/localstore: stop sending to errChan on context done in tests

* swarm/storage/localstore: better want check in readPullSubscriptionBin

* swarm/storage/localstore: protect chunk put with addr lock in tests

* swamr/storage/localstore: wait for gc and writeGCSize workers on Close

* swarm/storage/localstore: more correct testDB_collectGarbageWorker

* swarm/storage/localstore: set DB Close timeout to 5s