Clear logs

[sarahhodne]

In case of exposed credentials or other security issues, it would be nice if a user with some set privileges (push+ or admin, not sure which) can click a button to clear the logs attached to a given job (maybe even build).

This is similar to, but different from, #877, since that refers to deleting (or “archiving”) the entire build.

Functionality-wise, what this button would do is replace the content of the logs in the database with something similar to “This log has been removed” and re-archive it. While in general I prefer a “deleted” flag, or something other than plain removing content from the database (see this post), in this case I think I would go for just replacing the content in the database instead of a separate column since this feature would probably mostly be used with leaked credentials.

[sarahhodne]

Duplicate of #890.