[Core] Add way to check if a signal has any connections

Added to `Object` and `Signal`

scene/main/node.cpp

@@ -4019,4 +4019,9 @@ bool Node::is_connected(const StringName &p_signal, const Callable &p_callable)
 	return Object::is_connected(p_signal, p_callable);
 }
 
+bool Node::has_connections(const StringName &p_signal) const {
+	ERR_THREAD_GUARD_V(false);
+	return Object::has_connections(p_signal);
+}
+
 #endif