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

node/node.go

@@ -38,7 +38,7 @@ import (
 	rpccore "github.com/tendermint/tendermint/rpc/core"
 	ctypes "github.com/tendermint/tendermint/rpc/core/types"
 	grpccore "github.com/tendermint/tendermint/rpc/grpc"
-	rpcserver "github.com/tendermint/tendermint/rpc/lib/server"
+	rpcserver "github.com/tendermint/tendermint/rpc/jsonrpc/server"
 	sm "github.com/tendermint/tendermint/state"
 	"github.com/tendermint/tendermint/state/txindex"
 	"github.com/tendermint/tendermint/state/txindex/kv"
@@ -929,7 +929,7 @@ func (n *Node) startRPC() ([]net.Listener, error) {
 			rootHandler = corsMiddleware.Handler(mux)
 		}
 		if n.config.RPC.IsTLSEnabled() {
-			go rpcserver.StartHTTPAndTLSServer(
+			go rpcserver.ServeTLS(
 				listener,
 				rootHandler,
 				n.config.RPC.CertFile(),
@@ -938,7 +938,7 @@ func (n *Node) startRPC() ([]net.Listener, error) {
 				config,
 			)
 		} else {
-			go rpcserver.StartHTTPServer(
+			go rpcserver.Serve(
 				listener,
 				rootHandler,
 				rpcLogger,