Previously in https://chromium-review.googlesource.com/c/v8/v8/+/2545573
I updated BasicBlockInstrumentor to use 64-bit floating-point values
rather than 32-bit integers, so that it could never overflow. However,
I've now learned that some builtins (particularly RecordWrite) are not
allowed to use floating-point registers, and so running with
basic block instrumentation enabled could produce incorrect results.
This change switches back to 32-bit integers, but adds saturation logic.

Bug: chromium:1170776
Change-Id: Icbd93919fb05f50d615ec479263142addbe15c9e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2685617Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#72626}