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/framework/extender.go

@@ -50,6 +50,12 @@ type Extender interface {
 	// this pod is managed by this extender.
 	IsInterested(pod *v1.Pod) bool
 
+	// IsPrioritizer returns whether this extender is configured for the Prioritize method.
+	IsPrioritizer() bool
+
+	// IsFilter returns whether this extender is configured for the Filter method.
+	IsFilter() bool
+
 	// ProcessPreemption returns nodes with their victim pods processed by extender based on
 	// given:
 	//   1. Pod to schedule