Automatic merge from submit-queue (batch tested with PRs 42237, 42297, 42279, 42436, 42551)
Cleanup federation_util.go in e2e/framework
The only function GetValidDNSSubdomainName in test/e2e/framework/federation_util.go is no longer used for some time now. so cleaning it up.
cc @kubernetes/sig-federation-pr-reviews @madhusudancs