Workflow for cleaning up runner

[vmilosevic]

This workflow frees space on a runner by deleting the work folder and purging the docker cache.
Run workflow manually, choose cleanup options, and label the runner that is out of space.

Closes #196

[nvukobratTT]

Can we think about a more automatic way of doing this? E.g. is it possible to check the disk usage during initialization time, and do a cleanup like this?

[vmilosevic]

I'm afraid automating this will just hide problems and remove cached images and files too often. Let's have this workflow as emergency mitigation.

We should look into

• requesting more storage for our VMs
• reducing Docker image size

[nvukobratTT]

@vmilosevic similar question, let's track these as new issues, just not to lose track of it. Is it possible for you to create them in FFE repo?