.. now that all JSObjectRef methods can run in concurrent settings.

Also change a few subtypes to bg-serialized:

 - JSArray
 - JSGlobalProxy
 - JSTypedArray

Bug: v8:7790
Change-Id: I406b0a8eacb4e5bd2c3a24eb106b29df2cf55421
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2966377Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75452}