Initialize bit field in map using relaxed store

Map::bit_field needs to be set with relaxed store. The concurrent marker
accesses the has_prototype_slot bit in Map::bit_field to calculate
header size.

Bug: v8:10315
Change-Id: Ie7ebb9316b8c703adfddf10df25949b872ce0c8d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2194012Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67728}

src/objects/map.cc

@@ -1456,7 +1456,7 @@ Handle<Map> Map::RawCopy(Isolate* isolate, Handle<Map> map, int instance_size,
   Handle<HeapObject> prototype(map->prototype(), isolate);
   Map::SetPrototype(isolate, result, prototype);
   result->set_constructor_or_backpointer(map->GetConstructor());
-  result->set_bit_field(map->bit_field());
+  result->set_relaxed_bit_field(map->bit_field());
   result->set_bit_field2(map->bit_field2());
   int new_bit_field3 = map->bit_field3();
   new_bit_field3 = Bits3::OwnsDescriptorsBit::update(new_bit_field3, true);