This commit increases the number of backtracks before we fall back to
the experimental engine.  The previous limit was reached just before
irregexp finished in sunspider/string-tagcloud and
web-tooling-benchmark/coffeescript.  This meant that we aborted
execution and started over with a slower (but asymptotically faster)
engine just before we would've finished, causing a performance
regression.

Bug: chromium:1138975,v8:10765
Change-Id: I10a4b149300f88680084604310730ee91758bfa0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2479010
Commit-Queue: Martin Bidlingmaier <mbid@google.com>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70673}