The `.proto` file do not have the `nullable = false` annotation present on the `SynchronyParams` durations. This pull request updates the `SynchronyParams` to match the checked in proto files.  Note, this does not make the code buildable against the latest protos. This pull request was achieved by checking out all files _not relevant_ to the `SynchronyParams` and removing the new `TimeoutParams` from the the `params.proto` file. Future updates will add these back. 

This pull request also adds a `nil` check to the `pbParams.Synchrony` field in `ConsensusParamsFromProto`. Old versions of Tendermint will not have the `Synchrony` parameters filled in so this code would panic on startup.

We will fill in the empty fields with defaults, but per https://github.com/tendermint/tendermint/blob/master/docs/rfc/rfc-009-consensus-parameter-upgrades.md#only-update-hashedparams-on-hash-breaking-releases we will keep out of the hash during this release.

This pull request merges in the changes for implementing Proposer-based timestamps into `master`. The power was primarily being done in the `wb/proposer-based-timestamps` branch, with changes being merged into that branch during development. This pull request represents an amalgamation of the changes made into that development branch. All of the changes that were placed into that branch have been cleanly rebased on top of the latest `master`. The changes compile and the tests pass insofar as our tests in general pass.

### Note To Reviewers
 These changes have been extensively reviewed during development. There is not much new here. In the interest of making effective use of time, I would recommend against trying to perform a complete audit of the changes presented and instead examine for mistakes that may have occurred during the process of rebasing the changes. I gave the complete change set a first pass for any issues, but additional eyes would be very appreciated. 

In sum, this change set does the following:
closes #6942 
merges in #6849

The code in the Tendermint repository makes heavy use of import aliasing.
This is made necessary by our extensive reuse of common base package names, and
by repetition of similar names across different subdirectories.

Unfortunately we have not been very consistent about which packages we alias in
various circumstances, and the aliases we use vary. In the spirit of the advice
in the style guide and https://github.com/golang/go/wiki/CodeReviewComments#imports,
his change makes an effort to clean up and normalize import aliasing.

This change makes no API or behavioral changes. It is a pure cleanup intended
o help make the code more readable to developers (including myself) trying to
understand what is being imported where.

Only unexported names have been modified, and the changes were generated and
applied mechanically with gofmt -r and comby, respecting the lexical and
syntactic rules of Go.  Even so, I did not fix every inconsistency. Where the
changes would be too disruptive, I left it alone.

The principles I followed in this cleanup are:

- Remove aliases that restate the package name.
- Remove aliases where the base package name is unambiguous.
- Move overly-terse abbreviations from the import to the usage site.
- Fix lexical issues (remove underscores, remove capitalization).
- Fix import groupings to more closely match the style guide.
- Group blank (side-effecting) imports and ensure they are commented.
- Add aliases to multiple imports with the same base package name.

## Description

Add test vectors for all reactors

- [x] state-sync
- [x] privval
- [x] mempool
- [x] p2p
- [x] evidence
- [ ] light?

this PR is primarily oriented at testvectors for things going over the wire. should we expand the testvectors into types as well?

Closes: #XXX

## Description



Closes: #XXX

Fixes #828. Adds state sync, as outlined in [ADR-053](https://github.com/tendermint/tendermint/blob/master/docs/architecture/adr-053-state-sync-prototype.md). See related PRs in Cosmos SDK (https://github.com/cosmos/cosmos-sdk/pull/5803) and Gaia (https://github.com/cosmos/gaia/pull/327).

This is split out of the previous PR #4645, and branched off of the ABCI interface in #4704. 

* Adds a new P2P reactor which exchanges snapshots with peers, and bootstraps an empty local node from remote snapshots when requested.

* Adds a new configuration section `[statesync]` that enables state sync and configures the light client. Also enables `statesync:info` logging by default.

* Integrates state sync into node startup. Does not support the v2 blockchain reactor, since it needs some reorganization to defer startup.