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.

Remove `Context` from the `TxInfo` type and instead require the caller to pass a `Context` to `CheckTx` which is idiomatic.

closes: #6497

## Description

Internalize some libs. This reduces the amount ot public API tendermint is supporting. The moved libraries are mainly ones that are used within Tendermint-core.

allow ReapX and CheckTx functions to run in parallel, making it not possible to block certain proposers from creating a new block.

Closes: #2972

* mempool: moved TxInfo parameter into Mempool.CheckTx().

* Updated CHANGELOG_PENDING.md

* Added PR issue to CHANGELOG_PENDING

Fixes #3590

* mempool: remove only valid (Code==0) txs on Update

so evil proposers can't drop valid txs in Commit stage.

Also remove invalid (Code!=0) txs from the cache so they can be
resubmitted.

Fixes #3322

@rickyyangz:

In the end of commit stage, we will update mempool to remove all the txs
in current block.

// Update mempool.
err = blockExec.mempool.Update(
	block.Height,
	block.Txs,
	TxPreCheck(state),
	TxPostCheck(state),
)

Assum an account has 3 transactions in the mempool, the sequences are
100, 101 and 102 separately, So an evil proposal can only package the
101 and 102 transactions into its proposal block, and leave 100 still in
mempool, then the two txs will be removed from all validators' mempool
when commit. So the account lost the two valid txs.

@ebuchman:

In the longer term we may want to do something like #2639 so we can
validate txs before we commit the block. But even in this case we'd only
want to run the equivalent of CheckTx, which means the DeliverTx could
still fail even if the CheckTx passes depending on how the app handles
the ABCI Code semantics. So more work will be required around the ABCI
code. See also #2185

* add changelog entry and tests

* improve changelog message

* reformat code

## Description

Refs #2659

Breaking changes in the mempool package:

[mempool] #2659 Mempool now an interface
    old Mempool renamed to CListMempool
    NewMempool renamed to NewCListMempool
    Option renamed to CListOption
    MempoolReactor renamed to Reactor
    NewMempoolReactor renamed to NewReactor
    unexpose TxID method
    TxInfo.PeerID renamed to SenderID
    unexpose MempoolReactor.Mempool

Breaking changes in the state package:

[state] #2659 Mempool interface moved to mempool package
    MockMempool moved to top-level mock package and renamed to Mempool

Non Breaking changes in the node package:

[node] #2659 Add Mempool method, which allows you to access mempool

## Commits

* move Mempool interface into mempool package

Refs #2659

Breaking changes in the mempool package:

- Mempool now an interface
- old Mempool renamed to CListMempool

Breaking changes to state package:

- MockMempool moved to mempool/mock package and renamed to Mempool
- Mempool interface moved to mempool package

* assert CListMempool impl Mempool

* gofmt code

* rename MempoolReactor to Reactor

- combine everything into one interface
- rename TxInfo.PeerID to TxInfo.SenderID
- unexpose MempoolReactor.Mempool

* move mempool mock into top-level mock package

* add a fixme

TxsFront should not be a part of the Mempool interface
because it leaks implementation details. Instead, we need to come up
with general interface for querying the mempool so the MempoolReactor
can fetch and broadcast txs to peers.

* change node#Mempool to return interface

* save commit = new reactor arch

* Revert "save commit = new reactor arch"

This reverts commit 1bfceacd9d.

* require CListMempool in mempool.Reactor

* add two changelog entries

* fixes after my own review

* quote interfaces, structs and functions

* fixes after Ismail's review

* make node's mempool an interface

* make InitWAL/CloseWAL methods a part of Mempool interface

* fix merge conflicts

* make node's mempool an interface