Automatic merge from submit-queue

Listing pods only once when getting pods for RS in deployment

Fixes #26834

1. Avoid ranging over RSes and then `List` pods of each RS. Instead, `List` pods of the deployment once, and then filter pods of each RS. 
2. Avoid using clientset to `List` pods in deployment controller. Use podStore instead. (TODO in some functions because the unit tests don't have podStore.)

@kubernetes/deployment 

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