Remove reliance on github.com/openshift/generic-admission-server

[zhill]

The project's last release was in 2019, so it doesn't work with recent k8s versions.

This controller should remove reliance on that library and solve the API handling and setup/config another way.

[zhill]

For now, I've created a fork and updated the fork, but the upstream has many commits but no recent release. For now, I believe we can get things working that we need to without addressing this directly, but it is still important just not urgent.