test-oci-registry.sh: extend
test-oci-registry.sh: extend

Add:
 * Testing of flatpakrefs and bundles pointing to OCI remotes
 * Changing a remote from OCI to non-OCI, including during bundle
   installation.
 * Pruning origin remotes.

flatpak/flatpak,flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak