Until now, LABs were accessed from generated code via external
references, e.g., see NewSpaceAllocationTopAddress() and
NewSpaceAllocationLimitAddress().

This patch places them in the IsolateData, so they can be accessed
using Isolate-constant offsets. It affects the hot path of all TF
generated code.

Bug: v8:12428
Change-Id: I7bfd54bea4febead404829d8e0b058b6cf53a374
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3303800
Commit-Queue: Nikolaos Papaspyrou <nikolaos@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78176}