[heap] Make heap iterable in CollectCodeStatistics()

With LocalHeaps multiple threads may now access the heap. We now need
to bring background threads to a safepoint and make all LABs iterable
in order to be able to safely iterate the heap.

Bug: v8:12338
Change-Id: Ia39f3bf7ac13ba405c86ee2f0048c600ce36c2d8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3256690Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77670}

src/heap/heap.cc

@@ -4172,6 +4172,8 @@ std::unique_ptr<v8::MeasureMemoryDelegate> Heap::MeasureMemoryDelegate(
 
 void Heap::CollectCodeStatistics() {
   TRACE_EVENT0("v8", "Heap::CollectCodeStatistics");
+  SafepointScope safepoint_scope(this);
+  MakeHeapIterable();
   CodeStatistics::ResetCodeAndMetadataStatistics(isolate());
   // We do not look for code in new space, or map space.  If code
   // somehow ends up in those spaces, we would miss it here.