This implements a new `Transport` interface and related types for the P2P refactor in #5670. Previously, `conn.MConnection` was very tightly coupled to the `Peer` implementation -- in order to allow alternative non-multiplexed transports (e.g. QUIC), MConnection has now been moved below the `Transport` interface, as `MConnTransport`, and decoupled from the peer. Since the `p2p` package is not covered by our Go API stability, this is not considered a breaking change, and not listed in the changelog.

The initial approach was to implement the new interface in its final form (which also involved possible protocol changes, see https://github.com/tendermint/spec/pull/227). However, it turned out that this would require a large amount of changes to existing P2P code because of the previous tight coupling between `Peer` and `MConnection` and the reliance on subtleties in the MConnection behavior. Instead, I have broadened the `Transport` interface to expose much of the existing MConnection interface, preserved much of the existing MConnection logic and behavior in the transport implementation, and tried to make as few changes to the rest of the P2P stack as possible. We will instead reduce this interface gradually as we refactor other parts of the P2P stack.

The low-level transport code and protocol (e.g. MConnection, SecretConnection and so on) has not been significantly changed, and refactoring this is not a priority until we come up with a plan for QUIC adoption, as we may end up discarding the MConnection code entirely.

There are no tests of the new `MConnTransport`, as this code is likely to evolve as we proceed with the P2P refactor, but tests should be added before a final release. The E2E tests are sufficient for basic validation in the meanwhile.

## Description

Remove concurrent write access bug by removing the memoized string representation of a `NetAddress`.

Closes: #5047

## Description

migrate p2p/pex to protobuf

Closes: #XXX

Closes #4846 
Spec https://github.com/tendermint/spec/pull/96

Closes #4603

Commands used (VIM):

```
:args `rg -l errors.Wrap`
:argdo normal @q | update
```

where q is a macros rewriting the `errors.Wrap` to `fmt.Errorf`.

Refs #3262

Refs #3262

* p2p: extract ID validation into a separate func

- NewNetAddress panics if ID is invalid
- NetAddress#Valid returns an error
- remove ErrAddrBookInvalidAddrNoID

Fixes #2722

* p2p: remove repetitive check in ReceiveAddrs

* fix netaddress test

Fixes #3521

The function NewNetAddressStringWithOptionalID is from a time when peer
IDs were optional. They're not anymore. So this should be renamed to
NewNetAddressString and should ensure the ID is provided.

* update changelog
* use NewNetAddress in transport tests
* use NewNetAddress in TestTransportMultiplexAcceptMultiple

* Remove deprecated PanicXXX functions from codebase

As per discussion over
[here](https://github.com/tendermint/tendermint/pull/3456#discussion_r278423492),
we need to remove these `PanicXXX` functions and eliminate our
dependence on them. In this PR, each and every `PanicXXX` function call
is replaced with a simple `panic` call.

* add a changelog entry

* Revert to using defers in addrbook.  ValidateBasic->Validate since it requires DNS

* Update CHANGELOG_PENDING

* Require addressbook to only store addresses with valid ID

* Do not shut down peer immediately after sending pex addrs in SeedMode

* p2p: fix #2773

* seed mode: use go-routine to sleep before stopping peer

* require block.Time of the fist block to be genesis time

Refs #2587:

```
We only start validating block.Time when Height > 1, because there is no
commit to compute the median timestamp from for the first block. This
means a faulty proposer could make the first block with whatever time
they want.

Instead, we should require the timestamp of block 1 to match the genesis
time.

I discovered this while refactoring the ValidateBlock tests to be
table-driven while working on tests for #2560.
```

* do not accept blocks with negative height

* update changelog and spec

* nanos precision for test genesis time

* Fix failing test (#2607)

fix #2071

Signed-off-by: phymbert <pierrick.hymbert@gmail.com>

* libs: Remove usage of custom Fmt, in favor of fmt.Sprintf

Closes #2193

* Fix bug that was masked by custom Fmt!

This reverts commit d02c5d1e30.

This reverts commit 96a3502

Refs #1228

* use increment and decrement operators.

* remove unnecessary else branches.

* fix package comment with leading space.

* fix receiver names.

* fix error strings.

* remove omittable code.

* remove redundant return statement.

* Revert changes (code is generated.)

* use cfg as receiver name for all config-related types.

* use lsi as the receiver name for the LastSignedInfo type.

Fixes #934