[Feature Request]: Add support for Azure Firewall scaling options

### Which product(s) are you raising for?

ALZ Terraform (AVM)

### What is the feature request?

Add support in alz to set scaling options for Azure Firewall through configuration.

Seems like setting prescaling is not supported in AzureRM, and would need to refactor for az_api. Though would be helpfull to be able to also configure prescaling options.

https://learn.microsoft.com/en-gb/azure/firewall/prescaling

https://learn.microsoft.com/en-us/azure/templates/microsoft.network/azurefirewalls?pivots=deployment-language-terraform

### Potential implementation/configuration

```Text
Seems to only be supported through az_api.
```

Review the Azure Firewall prescaling documentation and Azure template reference first. Then trace the ALZ Terraform (AVM) configuration and assess the required AzureRM-to-az_api changes; done means scaling options, including prescaling where supported, can be configured through the project.

Written by the indexing model from the issue text.