Migrate chromium.android builders to set tests in starlark.

This migrates non-cronet builders in chromium.android that do not use
any matrix compound suites or suites that are intended to be kept in
sync with a matrix compound suite.

This also adds support for optional dimensions by handling converting
the integer keys to string for the json representation.

Bug: 40258588
Change-Id: Ide53993f0bf8c4dc98df52f242d1809bd9f4c022
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5805365
Reviewed-by: Struan Shrimpton <sshrimp@google.com>
Auto-Submit: Garrett Beaty <gbeaty@google.com>
Commit-Queue: Garrett Beaty <gbeaty@google.com>
Commit-Queue: Struan Shrimpton <sshrimp@google.com>
Cr-Commit-Position: refs/heads/main@{#1348348}