ci: fix auto-update charm libraries automated flow

[skatsaounis]

Add an intermediate check between update lib GH actions so that to avoid faulty behaviors when maas-region has an update and maas-agent does not.

[alema-r]

It should get the job done for now, but later we might want to propose some changes to the workflow from the observability team, to handle the libs update for more than one charm in the same repo.