Also, change its 'locals' field to a ZoneVector.
This is needed for 'let' as per [wasm-gc].

Bug: v8:7748
Change-Id: I9e6ca7f7e483b4bc13b64643107297be31af0e35
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2202995
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67847}