This allows the devtools to preview the private fields that are
installed on an object.

Change-Id: I6d8aad7ad0e51cdf18f6139b4bb8665e4b606aa5
Bug: v8:8773, v8:8337
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1487914
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Alexei Filippov <alph@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60134}