[Pixel Diff Ash] Include version numbers in benchmark names

Benchmark image names should include version numbers. For example,
when attempting to add a benchmark image whose name is Foo, the
developer should use "Foo.rev_0" instead of "Foo".

In addition, always increase the version number by 1 after each
update on benchmarks. For example, developer attempts to update the
benchmark "Foo.rev_0", after update, the benchmark name should be
"Foo.rev_1" instead of "Foo.rev_0".

This CL does not introduce any differences in product code.

Bug: 1383191
Change-Id: I04171b67d94b68d9b36f2aa55e29d66751052b1b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4016857
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Andrew Xu <andrewxu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1069881}