For accessors, instead of storing the descriptor index + holder in the
LoadHandler, store the getter directly (avoiding the
map->descriptor->pair->getter hops). For the non-prototype case, where
there's no LoadHandler, store the AccessorPair directly as a weak
handler instead of the Smi handler. We can't store the getter here
directly, because it could be in new space, and then we can't use it in
the stub cache.

Required some rejiggling of ic.cc method signatures, to allow
ComputeHandler to return a weak ref.

Change-Id: I22c0e64bec9880a3ba23c2d1eeb3a1c23179ca4b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3865557Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83059}