p2p: seed mode refactoring (#3011)

ListOfKnownAddresses is removed
panic if addrbook size is less than zero
CrawlPeers does not attempt to connect to existing or peers we're currently dialing
various perf. fixes
improved tests (though not complete)
move IsDialingOrExistingAddress check into DialPeerWithAddress (Fixes #2716)


* addrbook: preallocate memory when saving addrbook to file

* addrbook: remove oldestFirst struct and check for ID

* oldestFirst replaced with sort.Slice
* ID is now mandatory, so no need to check

* addrbook: remove ListOfKnownAddresses

GetSelection is used instead in seed mode.

* addrbook: panic if size is less than 0

* rewrite addrbook#saveToFile to not use a counter

* test AttemptDisconnects func

* move IsDialingOrExistingAddress check into DialPeerWithAddress

* save and cleanup crawl peer data

* get rid of DefaultSeedDisconnectWaitPeriod

* make linter happy

* fix TestPEXReactorSeedMode

* fix comment

* add a changelog entry

* Apply suggestions from code review

Co-Authored-By: melekes <anton.kalyaev@gmail.com>

* rename ErrDialingOrExistingAddress to ErrCurrentlyDialingOrExistingAddress

* lowercase errors

* do not persist seed data

pros:
- no extra files
- less IO

cons:
- if the node crashes, seed might crawl a peer too soon

* fixes after Ethan's review

* add a changelog entry

* we should only consult Switch about peers

checking addrbook size does not make sense since only PEX reactor uses
it for dialing peers!

https://github.com/tendermint/tendermint/pull/3011#discussion_r270948875

node/node.go

@@ -498,6 +498,12 @@ func NewNode(config *cfg.Config,
 			&pex.PEXReactorConfig{
 				Seeds:    splitAndTrimEmpty(config.P2P.Seeds, ",", " "),
 				SeedMode: config.P2P.SeedMode,
+				// See consensus/reactor.go: blocksToContributeToBecomeGoodPeer 10000
+				// blocks assuming 10s blocks ~ 28 hours.
+				// TODO (melekes): make it dynamic based on the actual block latencies
+				// from the live network.
+				// https://github.com/tendermint/tendermint/issues/3523
+				SeedDisconnectWaitPeriod: 28 * time.Hour,
 			})
 		pexReactor.SetLogger(logger.With("module", "pex"))
 		sw.AddReactor("PEX", pexReactor)