Do not rely on GPG key id

[Obihoernchen]

• use the key name if possible
• instead of downloading repomd.xml.key, create it on the fly

@gurevichmark please check if this works for your environment, too.

[Obihoernchen]

Added some EL9 related fixes

[gurevichmark]

@Obihoernchen
Appears to work in our regression environment.
I generated xcat-core ubuntu and rpm builds using consortium branch.
The regression runs of x86 rhel8.6 and x86 ubuntu18.04.02were successful using that build. I did not rebuildxcat-dep, the regression runs used existing xcat-dep` package.