SetInformers not called by Cloud-Controller-Manager for out-off-tree cloudprovider

[hello2mao]

What happened:
When using in-tree cloudprovider, SetInformers will be called by kube controller manager, but it does not work for out-off-tree cloudprovider.

See below at createCloudProvider

package app

func createCloudProvider(cloudProvider string, externalCloudVolumePlugin string, cloudConfigFile string,
	allowUntaggedCloud bool, sharedInformers informers.SharedInformerFactory) (cloudprovider.Interface, ControllerLoopMode, error) {
	
        ....

	if informerUserCloud, ok := cloud.(cloudprovider.InformerUser); ok {
		informerUserCloud.SetInformers(sharedInformers)
	}
	return cloud, loopMode, err
}

[hello2mao]

/sig cloud-provider
cc @andrewsykim hi, I create a PR trying to fix this. See #73075

[hello2mao]

Fix in #73075 , close.