To get there, also:

- Refactor AllocationSite serialization as necessary.

- Make some accessors on AllocationSite atomic.

- Add JSObjectRef::raw_properties_or_hash().

- Eliminate use of IsFastLiteral in JSCallReducer. It isn't really
  needed there and we want to have only a single piece of code
  traversing boilerplates. (We still have a separate traversal in the
  serializer but that will be removed soon.)

- Merge IsFastLiteral checks into JSCreateLowering's
  TryAllocateFastLiteral.
  Note: TryAllocateFastLiteral doesn't explicitly look at the
  boilerplate's elements kind beyond bailing out for
  DICTIONARY_ELEMENTS in the beginning. After that it looks only at
  the backing store instance type. There is no room for confusion
  because, while elements kind transitions can generally happen
  concurrently to TryAllocateFastLiteral, boilerplates can never
  transition to DICTIONARY_ELEMENTS (added a CHECK for that).

- Slightly adapt CompilationDependencies and remove obsolete comments.

- Fix JSHeapBroker::ClearReconstructibleData (clearing of Refs in
  stress mode) to exclude JSObjectRefs with extra data.

Bug: v8:7790
Change-Id: Iee1232d01e04bcd00db04d48f6e82064fce6ff62
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3008894
Commit-Queue: Georg Neis <neis@chromium.org>
Auto-Submit: Georg Neis <neis@chromium.org>
Reviewed-by: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75656}