Implement methods for retrieving running jobs

[mfocko]

Implement methods that yield respective jobs to be cancelled, i.e., after retriggering a Copr build, we should get a list of running Copr builds associated with the previous trigger.

Warning

There is a possible issue with retriggering via comments (as they are not the same trigger, i.e., there would be a need to map the PR ID / current commit hash to the latest running builds/tests with the same commit hash).

Considering packit/packit#2534, the methods should return lists of Copr build IDs or Testing Farm request IDs.

For the sake of this card, do not consider subsequent jobs. It will be handled by a follow-up issue.

TODO

• Parse the revisions (commit hashes) from the respective events
  • GitHub
    • both push to branch and push to PR contain before and after which are SHA hashes of the commits
  • GitLab
    • For MRs there should be an oldrev attribute
    • Pushes contain before and after in the same fashion as the GitHub
• Implement method that provides already running Copr build for the preceding event
• Implement method that provides already running Testing Farm runs for the preceding event