system-reinstall-bootc smarter SSH key search

[omertuc]

authorized SSH keys are not always simple in ~/.ssh/authorized_keys and may need to be retrieved with special binaries.

The system-reinstall-bootc crate (#1063) should be improved to support those cases

Originally posted by @cgwalters in #1063 (comment)

[cgwalters]

I think this is fixed by 870da95 right?

[ckyrouac]

fixed by #1146