rename plugin/pkg/client/auth/plugins.go package name to auth
add the plugin import line in client-gen
update import_known_versions for release_1_5 clientset
change copy.sh
This commit handles:
* Passing ID Token as Bearer token
* Refreshing of tokens using refresh-tokens
* Persisting refreshed tokens
* ability to add arbitrary extra scopes via config
* this is what enables the cross-client/azp stuff