[Azure] Enhance guard to handle High Availability scenario

[Anumita]

Currently in AKS and Arc, we are using only one replica of guard. As AKS provides a HA AKS scenario, we would like guard also to be highly available. For this, we would need multiple replicas of guard deployed. We would also need a highly consistent cache as the rbac decision needs to be consistent across replicas.

This issue is a feature request to handle high availability scenario in guard for Azure.

Design Doc: #314

Would love to get your feedback on the same.

[tamalsaha]

Thanks for the pr. I am thinking that given all Azure teams's contribution, it might make sense to make the process more formal. I have moved the project to its own GitHub repo so that is possible. Let me know what you think. We could also propose this to the CNCF Sandbox etc.