Download variant analysis results

[elenatanasoiu]

🚨 Please review this PR commit-by-commit.

What

Follow-up from this PR where we introduced a monitor to check on the status of the variant analysis.

We'd like to auto-download results from the variant analysis as they become ready.

Why

Based on a previous discussion while implementing the variant analysis monitor, we decided that we'd like to trigger separate commands for actually downloading the results rather than performing it in the same process as the monitor.

The reason for this is that it would delay the polling and isn't really connected to what the monitor is supposed to do.

Future

In a separate PR, we'll also change the monitor and manager in order to emit events to the UI. These will be the various states of a download.

Checklist

• [ ] CHANGELOG.md has been updated to incorporate all user visible changes made by this pull request.
• [ ] Issues have been created for any UI or other user-facing changes made by this pull request.
• [ ] [Maintainers only] If this pull request makes user-facing changes that require documentation changes, open a corresponding docs pull request in the github/codeql repo and add the ready-for-doc-review label there.