[JSON Trace Profile] Correctly identify GC thread

Currently, the thread that includes the garbage collection notification events is not correctly identified.
This means that in the JSON trace profile, the thread:

* is not renamed, as desired.
* is not sorted towards the top, as desired.

The thread is identified by its name, which has changed from "Service Thread" to "Notification Thread". This change updates the profile code accordingly.

In response to #18548 (comment)
Fixes EngFlow/bazel_invocation_analyzer#110

Closes #20299.

PiperOrigin-RevId: 585639069
Change-Id: Id4aadb5451839b5be07ac98428f9367764ff46ce

src/main/java/com/google/devtools/build/lib/profiler/ThreadMetadata.java

@@ -49,7 +49,7 @@ private static boolean isMainThread(String threadName) {
   }
 
   private static boolean isGCThread(String threadName) {
-    return threadName.equals("Service Thread");
+    return threadName.equals("Notification Thread");
   }
 
   private static String getReadableName(String threadName) {