When searching for a target map during map update, attempt to
update field representations in-place to the more general
representation, where possible.

Bug: chromium:1143772
Change-Id: I6a43c94910a1d2d8f8b0ad89048f94b51461f76c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2507715
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70887}