This CL changes the dispatch technique in the regex interpreter to
token-threaded dispatch, if computed gotos are supported by the
compiler. Otherwise old switch-based dispatch is still used
(e.g. for MSVC).

With computed gotos, less jumps will be emitted (no extra jump to
single branch point/begin of switch) and branch prediction will
be better because of no single branch point.

This CL improves performance on the RexBench Benchmark suite by ~10%.

Bug: v8:9575
Change-Id: I585ad824ff1cc595a5dfa8831ad66d6810d0119b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1733073Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Patrick Thier <pthier@google.com>
Cr-Commit-Position: refs/heads/master@{#63126}