Publish task logs from Taskcluster

[eu9ene]

We are especially interested in publishing the full training live.log as a file to W&B artifacts or logs (wherever it will be more convenient to view it).

This can be published when the run is finished. We can view the live log directly in Taskcluster. I assume we can publish the live log not only for training but also for evaluation steps since it will be a very similar mechanism (likely transform).