Upload logs to Sourcegraph when executing with src-cli

Created by: malomarrec

Now that running batch changes server-side is beta, server-side runs stream logs directly into the GUI. src-cli logs are local only, and never get exposed inside the GUI.

As a first step, can we upload logs to the GUI once a local run has ended? Could we even upload logs as soon as one workspace has executed?

Estimates are for a spike.