Rename HistogramBase::Sample to Sample32 in ash.

Add size to type name so the size is known without needing to lookup
the typedef.

Change `base::Histogram::Sample` and `base::HistogramBase::Sample` to `base::HistogramBase::Sample32`.

Changed occurrences under ash folders

Bug: 40899968

Change-Id: Iaaf142195a53fe14f1a2afd588ad14fa36190c33
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6172272
Commit-Queue: Ramon Cano Aparicio <rcanoaparicio@google.com>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1405941}