node, rpc: add ReadHeaderTimeout config option (#25338)

This change makes http.Server.ReadHeaderTimeout configurable separately
from ReadTimeout for RPC servers. The default is set to the same as
ReadTimeout, which in order to cause no change in existing deployments.

node/rpcstack.go

@@ -134,6 +134,7 @@ func (h *httpServer) start() error {
 	if h.timeouts != (rpc.HTTPTimeouts{}) {
 		CheckTimeouts(&h.timeouts)
 		h.server.ReadTimeout = h.timeouts.ReadTimeout
+		h.server.ReadHeaderTimeout = h.timeouts.ReadHeaderTimeout
 		h.server.WriteTimeout = h.timeouts.WriteTimeout
 		h.server.IdleTimeout = h.timeouts.IdleTimeout
 	}