INFRA: Azure ARM template - switch Azure OpenAI service to private endpoint

[janaka]

Is your feature request related to a problem? Please describe. Currently the ARM template deploys Azure OpenAI with public access switched on.

Describe the solution you'd like

Switch to config and use Azure OpenAI over a private endpoint / VNET so that traffic remains within the customer VPC

https://learn.microsoft.com/en-us/azure/cognitive-services/cognitive-services-virtual-networks?context=/azure/cognitive-services/openai/context/context

Describe alternatives you've considered n/a

Additional context Add any other context or screenshots about the feature request here.