Automatic merge from submit-queue

[Federation] Create a unique label and label selector for each replica set created by the replica sets E2E test.

Previously, each replica set created would use the same pod labels and replica set label selectors, so tests run in parallel could conflict with each other. This ensures that each replica set test has its own set of pods to work with.

This should fix the currently-very-flaky E2E test for weighted federated replica set preferences.