V8 implements a fast-path for RegExp.prototype.split which diverges
from the spec: instead of creating a new sticky regexp instance
`splitter` and running it in a loop, we reuse the existing non-sticky
regexp without looping through each character.

This works fine in most cases, but we run into issues when matching at
the very end of the string. According to the spec, matches at the end
of the string are impossible in @@split, but in our fast-path
implementation they can happen.

The obvious fix would be to remove our fast-path but this comes with
high performance costs. The fix implemented in this CL adds a special
flag to `exec` s.t. matches at the end of the string can be treated as
failures. This is only relevant for @@split.

Bug: chromium:1075514
Change-Id: Ifb790ed116793998d7aeb37e307f3f3f764023d3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2681950
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72644}