Move ScheduleAlgorithm to the core package.

This moves the type `ScheduleAlgorithm` from `pkg/scheduler/algorithm`
to `pkg/scheduler/core`. The reason for this move is to fix our import
dependency graph and allow predicate & priority types to be moved into
their appropriate packages.

The new location makes sense because `core` is the only package that
exports an implementation of this type.

pkg/scheduler/algorithm/scheduler_interface.go

@@ -72,20 +72,3 @@ type SchedulerExtender interface {
 	// is unavailable. This gives scheduler ability to fail fast and tolerate non-critical extenders as well.
 	IsIgnorable() bool
 }
-
-// ScheduleAlgorithm is an interface implemented by things that know how to schedule pods
-// onto machines.
-type ScheduleAlgorithm interface {
-	Schedule(*v1.Pod, NodeLister) (selectedMachine string, err error)
-	// Preempt receives scheduling errors for a pod and tries to create room for
-	// the pod by preempting lower priority pods if possible.
-	// It returns the node where preemption happened, a list of preempted pods, a
-	// list of pods whose nominated node name should be removed, and error if any.
-	Preempt(*v1.Pod, NodeLister, error) (selectedNode *v1.Node, preemptedPods []*v1.Pod, cleanupNominatedPods []*v1.Pod, err error)
-	// Predicates() returns a pointer to a map of predicate functions. This is
-	// exposed for testing.
-	Predicates() map[string]FitPredicate
-	// Prioritizers returns a slice of priority config. This is exposed for
-	// testing.
-	Prioritizers() []PriorityConfig
-}