Notify PRr through a comment when Testing Farm runs have finished

[Venefilyn]

Description

This can be a bit more generic, but in short I would like to get notified through a GitHub comment whenever the testing farm runs have completed (or timed out). That way, I can go away from the PR and get notified later on when the results are in rather than checking periodically what the status is

Internal Slack thread https://redhat-internal.slack.com/archives/C04MU29TES1/p1706018947464069

Benefit

We would get notified when we have results to view

Importance

Medium

What is the impacted category (job)?

Testing Farm tests

Workaround

• [ ] There is an existing workaround that can be used until this feature is implemented.

Participation

• [ ] I am willing to submit a pull request for this issue. (Packit team is happy to help!)