WIP: svupdater/lists: add support for labels

Labels are new generic approach to existing official boolean option. This removes that option and instead introduces flags that can symbol anything.

This implementation is just extension of existing one so everything is till returned all at once. Labels can be matched by name between various pkglists but that has to be done by user. Here info for labels is duplicated to every occurrence of that label.

Implements https://gitlab.labs.nic.cz/turris/turris-os-packages/issues/557

This references changes in https://gitlab.labs.nic.cz/turris/turris-os-packages/merge_requests/151