Replace a ZoneUnorderedMap with a ZoneMap in order to avoid
non-deterministic iteration order resulting in non-deterministic IR
and non-deterministic allocations during code assembly later. The
map in question is very small in practice so there should be no
performance regression.

Bug: v8:11894
Change-Id: Ic961102b45b3df28dafdece0cfb54ff5ef940d56
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3001348Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75529}