Since load elimination is only enabled for wasm-gc, we should use
LoadImmutable over LoadImmutableFromObject when possible. This is
possible for instance fields, which are always populated before the
start of function execution.

Bug: v8:11510, chromium:1279211
Change-Id: Ib11e8d19b91a16f509983378f74bdc4c3c2150ad
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3341522Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78390}