Replace UserIDRange/GroupIDRange by IDRange in internal type to reduce difference with external type.

We had IDRange in both types prior 9440a68744 commit that splitted it
into UserIDRange/GroupIDRange. Later, in c91a12d205 commit we had to
revert this changes because they broke backward compatibility but
UserIDRange/GroupIDRange struct left in the internal type.

This commit removes these leftovers and reduces the differences
between internal and external types.

pkg/security/podsecuritypolicy/util/util.go

@@ -164,12 +164,12 @@ func PSPAllowsFSType(psp *policy.PodSecurityPolicy, fsType policy.FSType) bool {
 }
 
 // UserFallsInRange is a utility to determine it the id falls in the valid range.
-func UserFallsInRange(id int64, rng policy.UserIDRange) bool {
+func UserFallsInRange(id int64, rng policy.IDRange) bool {
 	return id >= rng.Min && id <= rng.Max
 }
 
 // GroupFallsInRange is a utility to determine it the id falls in the valid range.
-func GroupFallsInRange(id int64, rng policy.GroupIDRange) bool {
+func GroupFallsInRange(id int64, rng policy.IDRange) bool {
 	return id >= rng.Min && id <= rng.Max
 }