Changes:
- Refactor all global base and offset computations into a single
  function and simplify GlobalGet and GlobalSet.
- Remove unneeded pointer arithmetic in the simd case. This enables the
  use of object operators, including LoadImmutableFromObject, which
  might enable more loads to be eliminated.

Bug: v8:11510

Change-Id: Ieab45fd9433863780bcfd6d4596786c08e3951a6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3320457Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78326}