* 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.

EDIT: Updated, see [comment below]( https://github.com/tendermint/tendermint/pull/6785#issuecomment-897793175)

This change adds a sketch of the `Debug` mode. 

This change adds a `Debug` struct to the node package. This `Debug` struct is intended to be created and started by a command in the `cmd` directory. The `Debug` struct runs the RPC server on the data directories: both the state store and the block store.

This change required a good deal of refactoring. Namely, a new `rpc.go` file was added to the `node` package. This file encapsulates functions for starting RPC servers used by nodes. A potential additional change is to further factor this code into shared code _in_ the `rpc` package. 

Minor API tweaks were also made that seemed appropriate such as the mechanism for fetching routes from the `rpc/core` package.

Additional work is required to register the `Debug` service as a command in the `cmd` directory but I am looking for feedback on if this direction seems appropriate before diving much further.

closes: #5908

instead of panicking
Closes #5529

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

Fixes a couple of test data races. `testing.T` is not concurrency-safe and should not be used in goroutines at all.

## 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

## Description

This PR updates golang-ci to latest and stops looking at master for the action. 

Closes: #XXX

...rrayHTTP 

Closes #5135

Also, wrote a test for WriteRPCResponseHTTPError and used it with correct status codes according to https://www.jsonrpc.org/historical/json-rpc-over-http.html#response-codes

## Description

this log message was marked as not useful and in the issue it was proposed to move it to debug. I am going with this path for now. After we have refactored the logger we shold go through the codebase in order to clean our log statements. 

Closes: #2101

## Description

partially cleanup in preparation for errcheck

i ignored a bunch of defer errors in tests but with the update to go 1.14 we can use `t.Cleanup(func() { if err := <>; err != nil {..}}` to cover those errors, I will do this in pr number two of enabling errcheck.

ref #5059

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