rpc: refactor lib folder (#4836)
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
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