node: allow websocket and HTTP on the same port (#20810)

This change makes it possible to run geth with JSON-RPC over HTTP and
WebSocket on the same TCP port. The default port for WebSocket
is still 8546. 

    geth --rpc --rpcport 8545 --ws --wsport 8545

This also removes a lot of deprecated API surface from package rpc.
The rpc package is now purely about serving JSON-RPC and no longer
provides a way to start an HTTP server.

rpc/websocket.go

@@ -38,13 +38,6 @@ const (
 
 var wsBufferPool = new(sync.Pool)
 
-// NewWSServer creates a new websocket RPC server around an API provider.
-//
-// Deprecated: use Server.WebsocketHandler
-func NewWSServer(allowedOrigins []string, srv *Server) *http.Server {
-	return &http.Server{Handler: srv.WebsocketHandler(allowedOrigins)}
-}
-
 // WebsocketHandler returns a handler that serves JSON-RPC to WebSocket connections.
 //
 // allowedOrigins should be a comma-separated list of allowed origin URLs.