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

* core: remove unnecessary fields in log

* core: bump blockchain database version

* core, les: remove unnecessary fields in txlookup

* eth: print db version explicitly

* core/rawdb: drop txlookup entry struct wrapper

* blockchain: more tests for sidechain import, fixes #19105

* core/blockchain: rework import of pruned canon blocks and canon-prepended sidechains

* core/blockchain: minor clarity change

* core/blockchain: remove unused method

cast limit.Cur (int64) to uint64, fix test and compilation error

The current loop continuation condition is always true as a uint8
is always being checked whether it is less than 255 (its maximum
value). Since the loop starts with the value 1, the loop termination
can be guarranteed to exit once the value overflows to 0.

* swarm/storage: increase mget timeout in common_test.go

 TestDbStoreCorrect_1k sometimes timed out with -race on Travis.

--- FAIL: TestDbStoreCorrect_1k (24.63s)
    common_test.go:194: testStore failed: timed out after 10s

* swarm: remove unused vars from TestSnapshotSyncWithServer

nodeCount and chunkCount is returned from setupSim and those values
we use.

* swarm: move race/norace helpers from stream to testutil

As we will need to use the flag in other packages, too.

* swarm: refactor TestSwarmNetwork case

Extract long running test cases for better visibility.

* swarm/network: skip TestSyncingViaGlobalSync with -race

As panics on Travis.

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x7e351b]

* swarm: run TestSwarmNetwork with fewer nodes with -race

As otherwise we always get test failure with `network_test.go:374:
context deadline exceeded` even with raised `Timeout`.

* swarm/network: run TestDeliveryFromNodes with fewer nodes with -race

Test on Travis times out with 8 or more nodes if -race flag is present.

* swarm/network: smaller node count for discovery tests with -race

TestDiscoveryPersistenceSimulationSimAdapters failed on Travis with
`-race` flag present. The failure was due to extensive memory usage,
coming from the CGO runtime. Using a smaller node count resolves the
issue.

=== RUN   TestDiscoveryPersistenceSimulationSimAdapter
==7227==ERROR: ThreadSanitizer failed to allocate 0x80000 (524288) bytes of clock allocator (error code: 12)
FATAL: ThreadSanitizer CHECK failed: ./gotsan.cc:6976 "((0 && "unable to mmap")) != (0)" (0x0, 0x0)
FAIL    github.com/ethereum/go-ethereum/swarm/network/simulations/discovery     804.826s

* swarm/network: run TestFileRetrieval with fewer nodes with -race

Otherwise we get a failure due to extensive memory usage, as the CGO
runtime cannot allocate more bytes.

=== RUN   TestFileRetrieval
==7366==ERROR: ThreadSanitizer failed to allocate 0x80000 (524288) bytes of clock allocator (error code: 12)
FATAL: ThreadSanitizer CHECK failed: ./gotsan.cc:6976 "((0 && "unable to mmap")) != (0)" (0x0, 0x0)
FAIL	github.com/ethereum/go-ethereum/swarm/network/stream	155.165s

* swarm/network: run TestRetrieval with fewer nodes with -race

Otherwise we get a failure due to extensive memory usage, as the CGO
runtime cannot allocate more bytes ("ThreadSanitizer failed to
allocate").

* swarm/network: skip flaky TestGetSubscriptionsRPC on Travis w/ -race

Test fails a lot with something like:
 streamer_test.go:1332: Real subscriptions and expected amount don't match; real: 0, expected: 20

* swarm/storage: skip TestDB_SubscribePull* tests on Travis w/ -race

Travis just hangs...

ok  	github.com/ethereum/go-ethereum/swarm/storage/feed/lookup	1.307s
keepalive
keepalive
keepalive

or panics after a while.

Without these tests the race detector job is now stable. Let's
invetigate these tests in a separate issue:
https://github.com/ethersphere/go-ethereum/issues/1245

* swarm/newtork: WIP Span request span until delivery and put

* swarm/storage: Introduce new trace across single fetcher lifespan

* swarm/network: Put span ids for sendpriority in context value

* swarm: Add global span store in tracing

* swarm/tracing: Add context key constants

* swarm/tracing: Add comments

* swarm/storage: Remove redundant fix for filestore

* swarm/tracing: Elaborate constants comments

* swarm/network, swarm/storage, swarm:tracing: Minor cleanup

* swarm/network: Logline to see handshake addr

* swarm/network: Replace remote ip in handshake uaddr

* swarm/network: Add test for enode uaddr rewrite method

* swarm/network: Remove redundance pointer return from sanitize

* swarm/network: Obeying the linting machine

* swarm/network: Add panic comment

(travis trigger take 1)

* swarm/network/stream: fix a goroutine leak in Registry

* swarm/network, swamr/network/stream: Kademlia close addr count and depth change chans

* swarm/network/stream: rename close channel to quit

* swarm/network/stream: fix sync between NewRegistry goroutine and Close method

Simplifies the transaction presense check to use a function to
determine if the transaction is present in the block provided
to trace, which originally had a redundant parenthesis and used
a `exist` flag to dictate control flow.

Package crypto works with or without cgo, which is great. However, to make it
work without cgo required setting the build tag `nocgo`. It's common to disable
cgo by instead just setting the environment variable `CGO_ENABLED=0`. Setting
this environment variable does _not_ implicitly set the build tag `nocgo`. So
projects that try to build the crypto package with `CGO_ENABLED=0` will fail. I
have done this myself several times. Until today, I had just assumed that this
meant that this package requires cgo.

But a small build tag change will make this case work. Instead of using `nocgo`
and `!nocgo`, we can use `!cgo` and `cgo`, respectively. The `cgo` build tag is
automatically set if cgo is enabled, and unset if it is disabled.

This changes default location of the data directory to use the LOCALAPPDATA
environment variable, resolving issues with remote home directories an improving
compatibility with Cygwin.

Fixes #2239 
Fixes #2237 
Fixes #16437

This corrects the previous change which broke the build and
was pushed by accident.

* swarm: Reinstate Pss Protocol add call through swarm service

* swarm: Even less self