This CL implements early SyntaxErrors for regular expressions. Early
errors are thrown when a malformed pattern is parsed, rather than when
the code first runs.

We do this by having the JS parser call into the regexp parser when
a regexp pattern is found. Regexps are expected to be relatively
rare, small, and cheap to parse - that's why we currently accept that
the regexp parser does unnecessary work (e.g. creating the AST
structures).

If needed, we can optimize in the future. Ideas:

- Split up the regexp parser to avoid useless work for syntax validation.
- Preserve parser results to avoid reparsing later.

Bug: v8:896
Change-Id: I3d1ec18c980ba94439576ac3764138552418b85d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3106647
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Patrick Thier <pthier@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76502}