cppgc: Prefinalizers scopes

Enable the prefinalizers scope and add a top level AtomicSweep scope
so that prefinalizers are accounted as part of sweeping.

Change-Id: I9dade6a2367d30d20395de30c3db84922fee5a49
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3306567Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78185}

src/heap/cppgc/prefinalizer-handler.cc

@@ -52,7 +52,9 @@ void PreFinalizerHandler::RegisterPrefinalizer(PreFinalizer pre_finalizer) {
 }
 
 void PreFinalizerHandler::InvokePreFinalizers() {
-  StatsCollector::DisabledScope stats_scope(
+  StatsCollector::EnabledScope stats_scope(heap_.stats_collector(),
+                                           StatsCollector::kAtomicSweep);
+  StatsCollector::EnabledScope nested_stats_scope(
       heap_.stats_collector(), StatsCollector::kSweepInvokePreFinalizers);
 
   DCHECK(CurrentThreadIsCreationThread());