rpc: enable compression on HTTP transport (#19997)

This change adds support for gzip encoding on HTTP responses.
Gzip encoding is used when the client sets the 'accept-encoding: gzip' header.
Original change by @brianosaurus, with fixes from @SjonHortensius.

rpc/http.go

@@ -216,6 +216,7 @@ func NewHTTPServer(cors []string, vhosts []string, timeouts HTTPTimeouts, srv ht
 	// Wrap the CORS-handler within a host-handler
 	handler := newCorsHandler(srv, cors)
 	handler = newVHostHandler(vhosts, handler)
+	handler = newGzipHandler(handler)
 
 	// Make sure timeout values are meaningful
 	if timeouts.ReadTimeout < time.Second {