Previously to this commit only quantifiers of the form /<x>*/, i.e.
arbitrarily often greedy repetition, were implemented.  Now a much
larger class is supported, e.g. + and ? and their non-greedy variants.
Because it came up repeatedly during the implementation, the commit also
adds the Label and DeferredLabel classes to patch JMP and FORK target
addresses more easily.

Still not supported are the following quantifiers:
- Possessive quantifiers, where I'm not entirely sure whether they could
  be implemented in principle. Re2 doesn't support them.
- Quantifiers with large but finite numbers for min and max numbers of
  repetitions, as in e.g. /<x>{9000, 90000}/. These are currently
  limited to some small value. This is because the body of such
  repetitions is unrolled explicitly, so the size of the bytecode is
  linear in the number of repetitions.

Cq-Include-Trybots: luci.v8.try:v8_linux64_fyi_rel_ng
Bug: v8:10765
Change-Id: Id04d893252588abb0f80c3cb33cfc707f6601ea0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2387575
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69759}