Local is used in other contexts as well, e.g. LocalIsolate or LocalHeap. Make it clear from the name that EvacuationAllocator is only used during collections.

Bug: v8:10315
Change-Id: I7483270aabc3dfe1fdecf0e77d1638c6711a8a2c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2137413Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67034}