[Network] Expose afcConfiguration (AFC endpoint) on az network firewall

### Preconditions

- [x] No need to upgrade Python SDK or the Python SDK is ready.

### Related command

az network firewall create
az network firewall update
az network firewall show

### Resource Provider

Microsoft.Network/azureFirewalls

### Description of Feature or Work Requested

Expose the afcConfiguration on the Azure Firewall resource (Azure Firewall for Containers endpoint), matching the new PowerShell support (PR #30001).

afcConfiguration carries the AFC endpoint configuration on an Azure Firewall. The CLI should:

- surface afcConfiguration in az network firewall show output, and

- expose it on az network firewall create / update if it is settable per the swagger (exact property/param name and shape should follow the spec).

Property name, type, and whether it is read-only vs settable are defined in the swagger PR below and mirrored by the PowerShell change.

### Minimum API Version Required

2025-09-01

### Swagger PR link / SDK link

https://github.com/Azure/azure-rest-api-specs/pull/42245

### Request Example

See the azureFirewalls examples in the swagger PR: https://github.com/Azure/azure-rest-api-specs/pull/42245/files

### Target Date

2026-08-30

### PM Contact

Suren.Jamiyanaa@microsoft.com

### Engineer Contact

samankal@microsoft.com

### Additional context

- PowerShell PR (reference behavior): https://github.com/Azure/azure-powershell/pull/30001

- Location: azure-firewall extension (same place as az network firewall)