Currently, RegExpResult builds match indices lazily using data stored
in hidden internal fields on the result object itself. Unfortunately,
if an internal field is deleted, it can cause these hidden fields
to migrate to a dictionary, making indexed lookup unsafe. This CL
forces slow but safe lookup for these fields when lazily building
indices.

Bug: v8:9548, chromium:1013133
Change-Id: Ide87d9ca6a73644ced3de8e35ecac26330d365e4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1871756Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Joshua Litt <joshualitt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64474}