Use seqeuence number to represent generation of equivalence cache.

- snapshot equivalence cache generation numbers before snapshotting the
scheduler cache
- skip update when generation does not match live generation
- keep the node and increment its generation to invalidate it instead of
deletion
- use predicates order ID as key to improve performance

pkg/scheduler/testing/fake_cache.go

@@ -106,8 +106,5 @@ func (f *FakeCache) Snapshot() *schedulercache.Snapshot {
 	return &schedulercache.Snapshot{}
 }
 
-// IsUpToDate is a fake method for testing
-func (f *FakeCache) IsUpToDate(*schedulercache.NodeInfo) bool { return true }
-
 // NodeTree is a fake method for testing.
 func (f *FakeCache) NodeTree() *schedulercache.NodeTree { return nil }