Revert "Revert of [regexp] Remove remainder of native RegExpExecStub (patchset #8 id:140001 of https://codereview.chromium.org/2752143003/ )"

This reverts commit da118ddf.

Erroneous double revert.

TBR=jgruber@chromium.org
NOTRY=true
NOPRESUBMIT=true
NOTREECHECKS=true

Change-Id: Iecabbb9b046e9c66cb86f9e9c5c6e0de6eab1c58
Reviewed-on: https://chromium-review.googlesource.com/484382Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44773}