When updating the dispatch tables, the other instances are often
generated from the same wire bytes, or there is only the one original
instance in that list of instances. In both cases we can avoid the
costly hash table lookup, and just use the signature index from the
originating module.

For big modules, this saves more than 50% of time for updating the
dispatch tables, and ~25% of overall instantiation time.

R=manoskouk@chromium.org

Bug: v8:12593
Change-Id: I356d5dd10f6c0738330e9a8d1cb27f60ff21215a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3432212Reviewed-by: Manos Koukoutos <manoskouk@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78941}