Add capability for "Virtual WAN Networking" resources - Connectivity Subscription

[matt-FFFFFF]

To improve alignment with the ARM reference implementation option, this issue outlines the requirement to add support for deploying an Azure Virtual WAN based hub as part of the connectivity capability.

This would align to the Contoso reference architecture, providing the option to easily scale to support multiple Azure regions and on-premises locations (any-to-any connectivity) as shown in the following figure:

The connectivity child module already has a placeholder for this capability to be added without making a breaking change to the module:

{
  settings = {
    hub_networks = [
      # (hub_network instance(s) hidden)
    ]
    vwan_hub_networks = [
      # (Placeholder for vwan_hub_networks instance(s) to be added)
    ]
    ddos_protection_plan = {
      # (child elements hidden)
    }
    dns = {
      # (child elements hidden)
    }
  }
  location = null
  tags     = null
  advanced = null
}

Need to agree on the resource to be deployed, and configuration schema used to control settings (aligned to that already being used for hub_networks = []