Add method to make LABs in all local heaps iterable and invoke this
function in Heap::MakeHeapIterable().

Bug: v8:10315
Change-Id: I6c8b1ea2337647f68995c13e6244d5ef0673b0e6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2230534Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68193}