[MP] Fix synchronizer init and reset

Fix set_multiplayer_authority not resetting the synchronizer.

Fix the reset function not clearing the watchers state.

Skip wrap around check for the first sync packet after reset.

modules/multiplayer/multiplayer_synchronizer.h

@@ -66,6 +66,7 @@ private:
 	uint64_t last_sync_usec = 0;
 	uint16_t last_inbound_sync = 0;
 	uint32_t net_id = 0;
+	bool sync_started = false;
 
 	static Object *_get_prop_target(Object *p_obj, const NodePath &p_prop);
 	void _start();