Ensure data backup is enabled using `backup_blob_container_uri` for Azure Analysis Services Servers

Disabling data backup for Azure Analysis Services Servers may lead to loss of sensitive data.

In Azure Console -

1. Open the Azure Portal and go to Analysis Services.
2. Select the Analysis Services instance you wish to edit.
3. Select Backups and set to Enabled.
4. Click Backup Storage: Not configured to configure the storage location.

In Terraform -

1. In the azurerm_analysis_services_server resource, set backup_blob_container_uri to a valid blob container.

References:
https://learn.microsoft.com/en-us/azure/analysis-services/analysis-services-backup
https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/analysis_services_server#backup_blob_container_uri