Automatic merge from submit-queue

Allow shareable resources for admission control plugins.

Changes allow admission control plugins to share resources. This is done via new PluginInitialization structure. The structure can be extended for other resources, for now it is an shared informer for namespace plugins (NamespiceLifecycle, NamespaceAutoProvisioning, NamespaceExists).

If a plugins needs some kind of shared resource e.g. client, the client shall be added to PluginInitializer and Wants methods implemented to every plugin which will use it.