Until now expired package data gets deleted daily by a cronjob. The
admin page shows the size of all packages and the size of unreferenced
data. The users (#25035, #20631) expect the deletion of this data if
they run the cronjob from the admin page but the job only deletes data
older than 24h.
This PR adds a new button which deletes all expired data.
![grafik](https://github.com/go-gitea/gitea/assets/1666336/b3e35d73-9496-4fa7-a20c-e5d30b1f6850)
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Co-authored-by: silverwind <me@silverwind.io>