Add AzFunctions' Scale Controller support for managed identity

[davidmrdavid]

Today, the MSSQL backend requires runtime-driven scaling to autoscale in Azure Functions when managed identity is used to connect to the DB.

This ticket tracks providing out of the box support for autoscaling with MSSQL in the Scale Controller.

[davidmrdavid]

When completing this work, we should update these docs to reflect that managed identity is fully supported with the MSSQL backend for Azure Functions: https://learn.microsoft.com/en-us/Azure/azure-functions/durable/durable-functions-storage-providers#comparing-storage-providers