Migrate rai policy to unified azure.yaml

[therealjohn]

The work in #8521 needs to be migrated to support the unified azure.yaml config once merged: #8675

[amitbhave10]

Also need to make sure we update:

1. Samples: https://github.com/microsoft-foundry/foundry-samples-pr/pull/526
2. Doc: https://github.com/MicrosoftDocs/azure-ai-docs-pr/pull/12722
3. Schema: Add generic policies list to AgentDefinition schema microsoft/AgentSchema#101