Comment 2 for bug 2002168

To anyone the core-dev team reading this:
the Pro Client has recently implemented exactly this feature: providing upgrade counts for installed packages. If you want, instead of bringing it from the cache as done in the MRs for this bug, we can change it to read the Pro Client data, as mentioned in the [Other info] section above.

Implementation would be more reliable and clean.

IMHO this would make update-notifier depend on u-a-t, but I don't think this is a big problem, given u-a-t is in minimal anyway.

Please let me know if you think it is ok to import and run the code from `uaclient`, and if it is fine to depend on the package for the counts.