This reduces the number of label indices accepted by {br_table} from the
full function body size to specifically 65520 labels. Note that TurboFan
already had a similar limitation on switches, but caused a crash during
compilation up until now. This change just makes the limit explicit and
avoids the crash during compilation.

R=clemensh@chromium.org
TEST=mjsunit/regress/wasm/regress-9759
BUG=v8:9759

Change-Id: I3a9a4406b19a7f98fc36707b3b946be846170a15
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1821457
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Backes [né Hammacher] <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63944}