`ujust update` needs to account for bootc

[castrojo]

Let's adjust ujust update to account for bootc. bootc will error out if the system has layered packaged so it needs to check if there's local layered packages on the system.

If there are, upgrade via the usual rpm-ostree, if there aren't upgrade via bootc.

Note that bootc currently needs root permissions, so this might block depending on how upstream expects bootc to behave, we may need to engage with upstream on the permissions, polkit rules, etc.