Clean up a couple of the StoreHandler methods returning Builtins to
directly return the Code object, so that it can be used as a handler
straight away without having to go via the MakeCodeHandler helper (which
wasn't making anything anymore).

Change-Id: I4976829d25e2bdad0cf41088b76121ac9b500cd5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3663083
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80720}