This is needed to open a PR on GitHub. This commit is being made so that
the PR can start off in a broken Actions state.

This also initially disables most non-Bazel workflows to make workflow
iteration faster and less impacting on other team members.

This introduces a new mechanism for passing lists of tests to sharded
test targets in CI, and hooks it up. No actual sharding is occurring
yet. This led to some simplifications in the CI workflow since the
script can be more dynamic in computing the full list of targets (which
also works around a previous bug with instrumentation tests being run).
Java proto lite also needed to be upgraded for the scripts to be able to
use it.

More testing/documentation needed as this functionality continues to
expand.

This simply partitions bucketed groups of targets into chunks of 10 for
each run. Only 3 buckets are currently retained to test sharding in CI
before introducing full support.

Fixes some caching bucket and output bugs. Also, introduces while loop &
keep_going to introduce resilience against app test build failures (or
just test failures in general).

Also, enable other workflows.

Note that CI shouldn't fully pass yet since some documentation and
testing needs to be added yet, but this is meant to be a more realistic
test of the CI environment before the PR is finished.

Adds a human-readable prefix to make the shards look a bit nicer.

Also, adds more fine-tuned partitioning to bucket & reduce shard counts
to improve overall timing. Will need to be tested in CI.

A newly computed variable wasn't updated to be used in an earlier
change.

Add docstrings for proto.

See
#3757 (comment)
for context.