MapSpace was using a separate FreeList implementation since all maps
have the save exact same size. Remove FreeListMap and use the regular
free list which is also used for the old space. This will allow to use
LABs in the map space.

Bug: v8:10315
Change-Id: I00cfcb260edb20f044ad74a24772f810e1f93afd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2442789Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70256}