If the following conditions hold:
1) value is kSentinel,
2) slot is on stack,
3) stack is allocated below 4GB,
then the generational barrier would be erroneously triggered for the
stack object object. This CL fixes it. At the same time, it aims to
simplify the code and potentially optimizes it (by having 'and' instead
of 'sub').

Bug: chromium:1029379
Change-Id: Iafd91d50b0a1c3d97647f7bf3643dfcc7e9fb48f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3608629Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80202}