UpdateDispatchTables is the hottest function during Wasm instantiation,
thus dehandlify it, as it does not allocate on the JS heap anyway. This
saves ~20% of instantiation time locally.

R=manoskouk@chromium.org

Bug: v8:12593
Cq-Include-Trybots: luci.v8.try:v8_linux_gc_stress_dbg_ng
Cq-Include-Trybots: luci.v8.try:v8_mac64_gc_stress_dbg_ng
Change-Id: Ifdd3f8fcd2e31950b591b179a62a0d397c41c339
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3429205Reviewed-by: Manos Koukoutos <manoskouk@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78904}