OCPBUGS-34568,OCPBUGS-35095: non-HA alert cases

Pulls in changes from [1], which refactors alerts to accomodate for
non-HA cases.

[1]: kubernetes-monitoring/kubernetes-mixin#1010

Signed-off-by: Pranshu Srivastava <[email protected]>

Author: rexagod

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## 4.20
 
 - [#2595](https://github.com/openshift/cluster-monitoring-operator/pull/2595) Multi-tenant support for KSM's CRS feature-set downstream.
+- [#2360](https://github.com/openshift/cluster-monitoring-operator/pull/2630) Make `KubeCPUOvercommit` and `KubeMemoryOvercommit` alerts accommodate for non-HA scenarios as well.
 
 ## 4.18