Add packit CI

[LecrisUT]

Add a packit workflow to test the builds in Fedora against the latest packages. This CI does:

• builds on every PR, commit to main and release in their own environments
• create a PR on rawhide after a release
• (downstream CI) trigger a build when a packit PR is merged

Some additional improvements that can be made:

• Build for epel10 also (maybe it is missing some dependencies). This can be used to gather the missing dependencies and request epel10 branching all at once
• Add tests for post packaging, e.g. testing that the -devel files work appropriately or tests that require internet connection

Requires:

• Packit onboarding
• @airsim copr group creation: https://pagure.io/fedora-infrastructure/issue/12586

Originally described here

[LecrisUT]

Marking as draft to prevent accidental merge until the CI is installed