Design doc:  https://bit.ly/3jEVgzz

We represent the indirect function table of a WasmInstanceObject at
index 0 like the rest of the tables, i.e., as the 0th element of the
instance's indirect_function_tables() field. For performance, we
maintain direct links from the instance to the contents of table 0
(indirect_function_table_{size, sig_ids, refs, targets} in
WasmInstanceObject).

Bug: v8:11510
Change-Id: Ice49fd855109051d304ef9033cac7a495b68ab8b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3246970
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77752}