Add cross subscription support for some built-in AMA related policies

[mitramcc]

Allow 6 policies to use cross subscription User Assignem Managed Identities to simplify the work on Management group scenarios.

The list of policies are:

• Assign Cross Subscription User-Assigned Managed Identity to Virtual Machine Scale Set
• Assign Cross Subscription User-Assigned Managed Identity to Virtual Machines
• Configure Linux virtual machines to run Azure Monitor Agent with cross subscription user-assigned managed identity-based authentication
• Configure Linux virtual machine scale sets to run Azure Monitor Agent with cross subscription user-assigned managed identity-based authentication
• Configure Windows virtual machines to run Azure Monitor Agent with cross subscription user-assigned managed identity-based authentication
• Configure Windows virtual machine scale sets to run Azure Monitor Agent with cross subscription user-assigned managed identity-based authentication

[mitramcc]

@microsoft-github-policy-service agree

[aschabus]

@mitramcc can you please shorten to policy display name to max 128 characters and the descriptions to max 512 characters.
See https://learn.microsoft.com/en-us/azure/governance/policy/concepts/definition-structure#display-name-and-description

[mitramcc]

@mitramcc can you please shorten to policy display name to max 128 characters and the descriptions to max 512 characters. See https://learn.microsoft.com/en-us/azure/governance/policy/concepts/definition-structure#display-name-and-description

Thank you @aschabus
I've just reviewed the Display Names and Descriptions.