Reland "[heap] Invoke GC callbacks in safepoint for shared GCs"

This is a reland of commit eeed2ebadb

Changes since revert:
- Disable test for builds that don't support shared heap.

Original change's description:
> [heap] Invoke GC callbacks in safepoint for shared GCs
>
> After a shared GC, trigger all registered callbacks while the global
> safepoint is active.
>
> Bug: chromium:1395117
> Change-Id: I16c61533d44fbeddda18414d2256203848420a99
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4079624
> Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
> Commit-Queue: Patrick Thier <pthier@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#84653}

Bug: chromium:1395117
Change-Id: I145dadac39d81342d7fbc2bad8b87f3518b0100e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4081130
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Patrick Thier <pthier@chromium.org>
Cr-Commit-Position: refs/heads/main@{#84687}

src/heap/heap.cc

@@ -1235,6 +1235,19 @@ void Heap::GarbageCollectionEpilogueInSafepoint(GarbageCollector collector) {
         GetGCTypeFromGarbageCollector(collector), current_gc_callback_flags_);
   });
 
+  if (isolate()->is_shared_heap_isolate()) {
+    isolate()->global_safepoint()->IterateClientIsolates(
+        [this, collector](Isolate* client) {
+          if (client->is_shared_heap_isolate()) return;
+          client->heap()->safepoint()->IterateLocalHeaps(
+              [this, collector](LocalHeap* local_heap) {
+                local_heap->InvokeGCEpilogueCallbacksInSafepoint(
+                    GetGCTypeFromGarbageCollector(collector),
+                    current_gc_callback_flags_);
+              });
+        });
+  }
+
 #define UPDATE_COUNTERS_FOR_SPACE(space)                \
   isolate_->counters()->space##_bytes_available()->Set( \
       static_cast<int>(space()->Available()));          \

test/mjsunit/mjsunit.status

@@ -1821,6 +1821,7 @@
 ['no_js_shared_memory', {
   'shared-memory/*': [SKIP],
   'regress/regress-crbug-1394741': [SKIP],
+  'regress/regress-crbug-1395117': [SKIP],
 }],  # 'no_js_shared_memory'
 
 ##############################################################################

test/mjsunit/regress/regress-crbug-1395117.js

@@ -0,0 +1,14 @@
+// Copyright 2022 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// Flags: --shared-string-table
+
+let o = {}
+let json_str = '[{"a": 2.1, "b": 1, "c": "hello"}, {"a": null, "b": 2, "c": {"a": 2.1, "b": 1.1, "c": "hello"}}]';
+// Internalize a bunch of strings to trigger a shared GC.
+for (let i=0; i<100; i++) {
+  let str = 'X'.repeat(100) + i;
+  o[str] = str;
+}
+JSON.parse('[{"a": 2.1, "b": 1, "c": "hello"}, {"a": null, "b": 2, "c": {"a": 2.1, "b": 1.1, "c": "hello"}}]');