Implement drop-down for workflow dispatch to build from other image tags

[renner0e]

so instead of building from aurora:stable we could do aurora:testing or aurora:beta. This would be nice for testing. Uploading these to the test bucket so we can prepare for plasma-setup/plasma login manager the F44 release.

This would also be nice to test changes that haven't yet made it into the stable release.

[inffy]

So we would need a testing branch in ublue-os/aurora if we would want to build "f44 pre-release builds" right?

beta we already have so we could propably use that too.

Maybe just create sub-issues under this one, so it would be easier to note down things what we would need to do