Scheduler first fit (#123384)

* Don't evaluate extra nodes if there's no score plugin defined

* Fix existing unit test (add no op scoring plugin)

* Add unit tests for no score plugin scenario

* address review comments

* add a test with non-filter, non-scoring extender

pkg/scheduler/testing/framework/fake_plugins.go

@@ -280,3 +280,13 @@ func NewFakePreScoreAndScorePlugin(name string, score int64, preScoreStatus, sco
 		}, nil
 	}
 }
+
+// NewEqualPrioritizerPlugin returns a factory function to build equalPrioritizerPlugin.
+func NewEqualPrioritizerPlugin() frameworkruntime.PluginFactory {
+	return func(_ context.Context, _ runtime.Object, _ framework.Handle) (framework.Plugin, error) {
+		return &FakePreScoreAndScorePlugin{
+			name:  "EqualPrioritizerPlugin",
+			score: 1,
+		}, nil
+	}
+}