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.

* rpc: Strip down the base RPC client interface.

Prior to this change, the RPC client interface requires implementing the entire
Service interface, but most of the methods of Service are not needed by the
concrete clients. Dissociate the Client interface from the Service interface.

- Extract only those methods of Service that are necessary to make the existing
  clients work.

- Update the clients to combine Start/Onstart and Stop/OnStop. This does not
  change what the clients do to start or stop. Only the websocket clients make
  use of this functionality anyway.

  The websocket implementation uses some plumbing from the BaseService helper.
  We should be able to excising that entirely, but the current interface
  dependencies among the clients would require a much larger change, and one
  that leaks into other (non-RPC) packages.

  As a less-invasive intermediate step, preserve the existing client behaviour
  (and tests) by extracting the necessary subset of the BaseService
  functionality to an analogous RunState helper for clients. I plan to obsolete
  that type in a future PR, but for now this makes a useful waypoint.

Related:
- Clean up client implementations.
- Update mocks.

Revert the JSON-RPC/WebSocket response serialization format to the
standard way (i.e. a single RPC response per WebSocket text message) to
avoid breaking clients.

Serialization format changes will be discussed in an upcoming ADR.

Closes: #5373

## Description

Enable errcheck linter throughout the codebase

Closes: #5059

## Description

Work towards enabling errcheck

ref #5059

* docs: goleveldb is much more stable now

Refs https://github.com/syndtr/goleveldb/issues/226#issuecomment-682495490

* rpc/core/events: make sure WS client receives every event

previously, if the write buffer was full, the response would've been
lost without any trace (log msg, etc.)

* rpc/jsonrpc/server: set defaultWSWriteChanCapacity to 1

Refs #3905
Closes #3829

setting write buffer capacity to 1 makes transactions count per block
more stable and also reduces the pauses length by 20s.

before: https://github.com/tendermint/tendermint/issues/3905#issuecomment-681854328 net.Read - 20s
after: net.Read - 0.66s

* rpc/jsonrpc/server: buffer writes and avoid io.ReadAll during read

Migrates the `rpc` package to use new JSON encoder in #4955. Branched off of that PR.

Tests pass, but I haven't done any manual testing beyond that. This should be handled as part of broader 0.34 testing.

Closes https://github.com/tendermint/tendermint/issues/3857

Moves `lib/` folder to `jsonrpc/`.

Renames:

**packages**

`rpc` package -> `jsonrpc` package
`rpcclient` package -> `client` package
`rpcserver` package -> `server` package

**structs and interfaces**

```
JSONRPCClient to Client
JSONRPCRequestBatch to RequestBatch
JSONRPCCaller to Caller
```

**functions**

```
StartHTTPServer to Serve
StartHTTPAndTLSServer to ServeTLS

rpc/jsonrpc/client: rename NewURIClient to NewURI

NewJSONRPCClient to New
NewJSONRPCClientWithHTTPClient to NewWithHTTPClient
NewWSClient to NewWS
```

**misc**

- unexpose `ResponseWriterWrapper`
- remove unused http_params.go

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`.

Using the WebSocket server, when the same client calls multiple time the subscribe method, only the last subscription receives all the events of the previous ones.

example:

    subscription1 = tm.event = 'NewBlock'
    subscription2 = tm.event = 'Tx'

In this case, subscription2 will receive the new blocks but subscription1 will not.

This came from the WebSocket handler that had the declaration of the rpcrequest moved and so overridden for every request and given in the JSONReq client context (so the id of the subscription was not the right one).

This fixes the issue by simply declaring the rpcrequest inside the loop so every request will create a new object without overwriting the previous one.

* libs/common: refactor libs common 3

- move nil.go into types folder and make private
- move service & baseservice out of common into service pkg

ref #4147

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

* add changelog entry

https://www.jsonrpc.org/specification

What is done in this PR:

    JSONRPCClient: validate that Response.ID matches Request.ID I wanted
    to do the same for the WSClient, but since we're sending events as
    responses, not notifications, checking IDs would require storing
    them in memory indefinitely (and we won't be able to remove them
    upon client unsubscribing because ID is different then).

    Request.ID is now optional. Notification is a Request without an ID.
    Previously "" or 0 were considered as notifications

    Remove #event suffix from ID from an event response (partially fixes
    #2949) ID must be either string, int or null AND must be equal to
    request's ID. Now, because we've implemented events as responses, WS
    clients are tripping when they see Response.ID("0#event") !=
    Request.ID("0"). Implementing events as requests would require a lot
    of time (~ 2 days to completely rewrite WS client and server)

    generate unique ID for each request

    switch to integer IDs instead of "json-client-XYZ"
    id=0 method=/subscribe
    id=0 result=...
    id=1 method=/abci_query
    id=1 result=...

> send events (resulting from /subscribe) as requests+notifications (not
responses)

this will require a lot of work. probably not worth it

* rpc: generate an unique ID for each request
in conformance with JSON-RPC spec

* WSClient: check for unsolicited responses

* fix golangci warnings

* save commit

* fix errors

* remove ID from responses from subscribe
Refs #2949

* clients are safe for concurrent access

* tm-bench: switch to int ID

* fixes after my own review

* comment out sentIDs in WSClient
see commit body for the reason

* remove body.Close
it will be closed automatically

* stop ws connection outside of write/read routines
also, use t.Rate in tm-bench indexer when calculating ID

fix gocritic issues

* update swagger.yaml

* Apply suggestions from code review

* fix stylecheck and golint linter warnings

* update changelog

* update changelog2