[Core] Improve raylet failure error msg (#10345)

* Improve error message.

* Lint.

* Addressed code review.

src/ray/raylet/node_manager.cc

@@ -766,7 +766,10 @@ void NodeManager::NodeRemoved(const GcsNodeInfo &node_info) {
 
   RAY_CHECK(node_id != self_node_id_)
       << "Exiting because this node manager has mistakenly been marked dead by the "
-      << "monitor.";
+      << "monitor: GCS didn't receive heartbeats within timeout "
+      << RayConfig::instance().num_heartbeats_timeout() *
+             RayConfig::instance().raylet_heartbeat_timeout_milliseconds()
+      << " ms. This is likely since the machine or raylet became overloaded.";
 
   // Below, when we remove node_id from all of these data structures, we could
   // check that it is actually removed, or log a warning otherwise, but that may