When given a sticky regexp s.t. lastIndex > subject.length, the
following should happen:

1. exec returns null (= no match)
2. lastIndex is reset to 0.

This is usually done by the RegExp.p.exec builtin; but in some cases
we take different paths and try to re-implement the parts of exec that
we need.

One of these cases was in %StringReplaceNonGlobalRegExpWithFunction.
Here, we set lastIndex to 0 but then incorrectly called into
RegExpImpl::Exec. REI::Exec started matching with lastIndex == 0,
which is just plain wrong. With this CL we now correctly omit the
REI::Exec call and return null.

Bug: chromium:937681, v8:5361
Change-Id: I6bb1114a6b92ed3c6e63ec7f6ec2df4b95a19b4c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1514679Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60169}