## Description

This PR wraps the stdlib sync.(RW)Mutex & godeadlock.(RW)Mutex. This enables using go-deadlock via a build flag instead of using sed to replace sync with godeadlock in all files

Closes: #3242

* close peer's connection to avoid fd leak

Fixes #2967

* rename peer#Addr to RemoteAddr

* fix test

* fixes after Ethan's review

* bring back the check

* changelog entry

* write a test for switch#acceptRoutine

* increase timeouts? :(

* remove extra assertNPeersWithTimeout

* simplify test

* assert number of peers (just to be safe)

* Cleanup in OnStop

* run tests with verbose flag on CircleCI

* spawn a reading routine to prevent connection from closing

* get port from the listener

random port is faster, but often results in

```
panic: listen tcp 127.0.0.1:44068: bind: address already in use [recovered]
        panic: listen tcp 127.0.0.1:44068: bind: address already in use

goroutine 79 [running]:
testing.tRunner.func1(0xc0001bd600)
        /usr/local/go/src/testing/testing.go:792 +0x387
panic(0x974d20, 0xc0001b0500)
        /usr/local/go/src/runtime/panic.go:513 +0x1b9
github.com/tendermint/tendermint/p2p.MakeSwitch(0xc0000f42a0, 0x0, 0x9fb9cc, 0x9, 0x9fc346, 0xb, 0xb42128, 0x0, 0x0, 0x0, ...)
        /home/vagrant/go/src/github.com/tendermint/tendermint/p2p/test_util.go:182 +0xa28
github.com/tendermint/tendermint/p2p.MakeConnectedSwitches(0xc0000f42a0, 0x2, 0xb42128, 0xb41eb8, 0x4f1205, 0xc0001bed80, 0x4f16ed)
        /home/vagrant/go/src/github.com/tendermint/tendermint/p2p/test_util.go:75 +0xf9
github.com/tendermint/tendermint/p2p.MakeSwitchPair(0xbb8d20, 0xc0001bd600, 0xb42128, 0x2f7, 0x4f16c0)
        /home/vagrant/go/src/github.com/tendermint/tendermint/p2p/switch_test.go:94 +0x4c
github.com/tendermint/tendermint/p2p.TestSwitches(0xc0001bd600)
        /home/vagrant/go/src/github.com/tendermint/tendermint/p2p/switch_test.go:117 +0x58
testing.tRunner(0xc0001bd600, 0xb42038)
        /usr/local/go/src/testing/testing.go:827 +0xbf
created by testing.(*T).Run
        /usr/local/go/src/testing/testing.go:878 +0x353
exit status 2
FAIL    github.com/tendermint/tendermint/p2p    0.350s
```

This is the implementation for the design described in ADR 12[0]. It's
the first step of a larger refactor of the p2p package as tracked in
interface bundling all concerns of low-level connection handling and
isolating the rest of peer lifecycle management from the specifics of
the low-level internet protocols. Even if the swappable implementation
will never be utilised, already the isolation of conn related code in
one place will help with the reasoning about execution path and
addressation of security sensitive issues surfaced through bounty
programs and audits.

We deliberately decided to not have Peer filtering and other management
in the Transport, its sole responsibility is the translation of
connections to Peers, handing those to the caller fully setup. It's the
responsibility of the caller to reject those and or keep track. Peer
filtering will take place in the Switch and can be inspected in a the
following commit.

This changeset additionally is an exercise in clean separation of logic
and other infrastructural concerns like logging and instrumentation. By
leveraging a clean and minimal interface. How this looks can be seen in
a follow-up change.

Design #2069[2]
Refs #2067[3]
Fixes #2047[4]
Fixes #2046[5]

changes:
* describe Transport interface
* implement new default Transport: MultiplexTransport
* test MultiplexTransport with new constraints
* implement ConnSet for concurrent management of net.Conn, synchronous
to PeerSet
* implement and expose duplicate IP filter
* implemnt TransportOption for optional parametirisation

[0] https://github.com/tendermint/tendermint/blob/master/docs/architecture/adr-012-peer-transport.md
[1] https://github.com/tendermint/tendermint/issues/2067
[2] https://github.com/tendermint/tendermint/pull/2069
[3] https://github.com/tendermint/tendermint/issues/2067
[4] https://github.com/tendermint/tendermint/issues/2047
[5] https://github.com/tendermint/tendermint/issues/2046