This reverts commit 29379945.

Reason for revert: Needed for other revert:
https://chromium-review.googlesource.com/c/v8/v8/+/1145431

Original change's description:
> [cleanup] Rename {kLastErrorMessage} to {kNumberOfReasons}
> 
> The name {kLastErrorMessage} is misleading, as it's not actually the
> index of the last message (or reason), but one more (i.e. number of
> messages / reasons). Thus this renaming.
> 
> R=​mstarzinger@chromium.org
> 
> Bug: v8:7754
> Change-Id: Id21edcecac84c0e6068423c6124ef2881116dc7c
> Reviewed-on: https://chromium-review.googlesource.com/1145305
> Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#54593}

TBR=mstarzinger@chromium.org,clemensh@chromium.org

Change-Id: I2af83f4a2299e05ad9bcacfe69c0b483fd1488de
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7754
Reviewed-on: https://chromium-review.googlesource.com/1145520Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54596}