[heap] Introduce enum of garbage collection reasons.

src/extensions/statistics-extension.cc

Index: src/extensions/statistics-extension.cc
diff --git a/src/extensions/statistics-extension.cc b/src/extensions/statistics-extension.cc
index 5aafb7a9748bff24f4d7fc2b56684b2834cf1904..222820e0ac6db2658c8e6641209eba094c42406a 100644
--- a/src/extensions/statistics-extension.cc
+++ b/src/extensions/statistics-extension.cc
@@ -67,7 +67,8 @@ void StatisticsExtension::GetCounters(
         args[0]
             ->BooleanValue(args.GetIsolate()->GetCurrentContext())
             .FromMaybe(false)) {
-      heap->CollectAllGarbage(Heap::kNoGCFlags, "counters extension");
+      heap->CollectAllGarbage(Heap::kNoGCFlags,
+                              GarbageCollectionReason::kCountersExtension);
     }
   }