Add info metrics collector

[joneug]

This patch adds a collector providing the pyCA version and timestamp of the last sync with the upstream server.

In order to implement this, I added a __version__ module attribute, as suggested by PEP 396.

[coveralls]

Coverage decreased (-0.03%) to 90.75% when pulling 4649e6a21d1a021760c728923da6e608ead177e8 on joneug:info_collector into f71f178f52891947617998f92857dfccea23d895 on opencast:main.

[github-actions[bot]]

This pull request has conflicts, please resolve those before we can evaluate the pull request.

[lkiesow]

This has open change requests, has conflicts and is open forever. Closing this for now. In case the work on this continues, please just re-open the pull request.-