[FIXED JENKINS-18660] Added dedicated denormalized counter function

(cherry picked from commit 5981ac4ed7b4b5c462a71ae186a133f7fe44e1a1)

Conflicts:
	core/src/main/java/hudson/model/Label.java
Restrict new public API member(s) from 5981ac4ed7b4b5c462a71ae186a133f7fe44e1a1 cherry-picked as 9bee3ba75d80115456732e9791ba9caab71c9042