add(KEP-4247): Per-plugin callback functions for efficient enqueueing in the scheduling queue (kubernetes#4256)

* add(KEP-4247): Per-plugin callback functions for efficient enqueueing in the scheduling queue

* fix by review comments

* mark boxes

* fix based on reviews

* update toc

* fix based on reviews

* update toc

* fix based on reviews

* update toc

* fix by review

Author: sanposhiho

keps/prod-readiness/sig-scheduling/4247.yaml

@@ -0,0 +1,3 @@
+kep-number: 4247
+beta:
+  approver: "@wojtek-t"