Remove deprecated discovery/ServerResources function

ServerResources function was deprecated and instead ServerGroupsAndResources
function is suggested.

This PR removes ServerResources function and move every place to use ServerGroupsAndResources.

pkg/controlplane/instance_test.go

@@ -354,7 +354,7 @@ func TestStorageVersionHashes(t *testing.T) {
 		ContentConfig: restclient.ContentConfig{NegotiatedSerializer: legacyscheme.Codecs},
 	}
 	discover := discovery.NewDiscoveryClientForConfigOrDie(c)
-	all, err := discover.ServerResources()
+	_, all, err := discover.ServerGroupsAndResources()
 	if err != nil {
 		t.Error(err)
 	}