Revert of [turbofan] Speculatively optimize string character access. (patchset #1 id:1 of https://codereview.chromium.org/2905623003/ )

Reason for revert:
Changes layout tests:
https://build.chromium.org/p/client.v8.fyi/builders/V8-Blink%20Linux%2064/builds/15867

See:
https://github.com/v8/v8/wiki/Blink-layout-tests

Original issue's description:
> [turbofan] Speculatively optimize string character access.
>
> Add a protector cell for string bounds checks that is being used to
> protect speculative bounds for String.prototype.charCodeAt and
> String.prototype.charAt in TurboFan (and Crankshaft). This way we don't
> have the diamond in optimized code, which stands in the way of other
> optimizations for charCodeAt that are currently being worked on by
> petermarshall@.
>
> BUG=v8:6391
> TBR=mlippautz@chromium.org
> R=petermarshall@chromium.org
>
> Review-Url: https://codereview.chromium.org/2905623003
> Cr-Commit-Position: refs/heads/master@{#45514}
> Committed: https://chromium.googlesource.com/v8/v8/+/9d8bd0551657d60c66b2f96544eecedfba1cba8a

TBR=petermarshall@chromium.org,mlippautz@chromium.org,bmeurer@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:6391

Review-Url: https://codereview.chromium.org/2900333002
Cr-Commit-Position: refs/heads/master@{#45521}