apt backend is really slow

[umlaeute]

ideally, we would build a cache (e.g. on startup, or with some more sophisticated heuristics) that makes package search with apt blazingly fast.

[umlaeute]

actually, we are already using python3-apt to handle the cache for us...

since python3-apt does not really give us a view on the data (just an interface to the data), and deken-xtra-apt-helper.py is re-started for each search, it think there is little we can do to speed this up "even more" (the new helper is already quite fast compared to the original implementation)