Map::Hash relies on the fact that the map space is never compacted.
However this might change in the future, so instead of using the
address of the prototype's map, we use the prototype's identity hash
instead.

Bug: v8:12578
Change-Id: Ia4961ed55119681c0033aa187789f6710ff2d22c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3412085Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78768}