Automatic merge from submit-queue (batch tested with PRs 47204, 46808, 47432, 47400, 47099)
Make the generic webhook admission controller use the dynamic webhook config manager
Based on #46672 and #46388.
Only the last commit is unique.
* removed `SetWebhookSource` from the PluginInitializer
* implemented `SetExternalClientset` for the generic webhook admisson controller, initializing an ExternalWebhookConfigurationManager in the method.
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