Extend the flag parameter with a bit that decides if the input should
be converted (-0 to 0, and a string to the array index it represents).
Instruct redundancy elimination to never replace x with CheckBounds(x)
when this CheckBounds is of the converting kind.

Bug: chromium:1070892, chromium:1071743
Change-Id: I3125a6e267d56dae6bf6cb2f5f52d27ef65d7c79
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2157365
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67408}