WIP for minimizing symbolication requests
Combine requests where possible.
Be smarter about requesting symbols.

Find all unique symbols first, then fetch them each once. This
reduces the number of symbolication requests by a lot, and speeds
things up dramatically.
Use the correct code path in S3
Exit non-zero if we fail to fetch some symbols.

We can detect non-zero exits and include more logs in the job
output.
Limit to nightly channel.

All the chromeHangs data is from nightly builds, so we can limit
the analysis to that channel.