AMA Updates

[arjenhuitema]

Overview/Summary

Introduces the use of a single centralized User Assigned Managed Identity for AMA. Policy and Initiative assignments have been updated with new parameters.

This PR fixes/adds/changes/removes

• Updated the following built-in policy initiatives to support single User-Assigned Managed Identities (UAMI):
  • Enable Azure Monitor for VMs with Azure Monitoring Agent(AMA)
  • Enable Azure Monitor for VMSS with Azure Monitoring Agent(AMA)
  • Configure SQL VMs and Arc-enabled SQL Servers to install Microsoft Defender for SQL and AMA with a user-defined LA workspace
  • [Preview]: Enable ChangeTracking and Inventory for virtual machines
  • [Preview]: Enable ChangeTracking and Inventory for virtual machine scale sets
• Custom Defender for SQL initiative has been deprecated and is replaced by Configure SQL VMs and Arc-enabled SQL Servers to install Microsoft Defender for SQL and AMA with a user-defined LA workspace
• Custom User Assigned Managed Identity policy has been deprecated. UAMI for AMA is now centrally deployed therefore this policy is no longer required.

As part of this Pull Request I have

• [x] Checked for duplicate Pull Requests
• [x] Associated it with relevant issues, for tracking and closure.
• [x] Ensured my code/branch is up-to-date with the latest changes in the main branch
• [x] Performed testing and provided evidence.
• [x] Ensured contribution guidance is followed.
• [x] Updated relevant and associated documentation.
• [x] Updated the "What's New?" wiki page (located: /docs/wiki/whats-new.md)