refactor: Add gateway udt and add allowed values

[oZakari]

Overview/Summary

Create UDT for virtual network gateway parameters and add allowed values. In particular, with the consolidation and migration of the SKUS to default to availability zones per https://learn.microsoft.com/en-us/azure/vpn-gateway/gateway-sku-consolidation

Related Issues/Work Items

Fixes AB#37804

This PR fixes/adds/changes/removes

1. Adds UDT with allowed values
2. Fix sample bicep module

Breaking Changes

Notice: Breaking Changes in Bicep Module Configuration

As part of the migration to user-defined types (UDTs) for properties within the parVpnGatewayConfig and parExpressRouteGatewayConfig parameters, the following breaking changes have been introduced:

1. Supported SKUs Limited to Availability Zones

The list of supported SKUs for VPN and ExpressRoute gateways now only includes those with availability zones. This change aligns with the consolidation and migration updates outlined in the official Azure documentation. For more details, refer to the Gateway SKU Consolidation and Migration Guide.

2. Property Name Alignment for parVpnGatewayConfig

The generation property in parVpnGatewayConfig has been renamed to vpnGatewayGeneration to align with the schema property name already used for parExpressRouteGatewayConfig.

3. Case Sensitivity of bgpSettings

The bgpsettings property is now case-sensitive and must be written as bgpSettings.

Subproperty Changes:

• The asn and peerweight subproperties within bgpSettings now require integer values instead of strings, ensuring consistency with the resource schema.

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Please update your configurations accordingly to avoid deployment errors.

Testing Evidence

Replace this with any testing evidence to show that your Pull Request works/fixes as described and planned (include screenshots, if appropriate).

As part of this Pull Request I have

• Read the Contribution Guide and ensured this PR is compliant with the guide
• Ensured the resource API versions in .bicep file/s I am adding/editing are using the latest API version possible
• Checked for duplicate Pull Requests
• Associated it with relevant GitHub Issues
• (ALZ Bicep Core Team Only) Associated it with relevant ADO Items
• Ensured my code/branch is up-to-date with the latest changes in the main branch
• Performed testing and provided evidence.
• Updated one or more of the following tests (if required)
  • Unit
  • Linting
  • E2E (End-To-End)
  • ValidateAzCloud (Base validation in Azure Cloud)
  • ValidateMcCloud (Base validation in Azure China Cloud)
• Updated relevant and associated documentation (e.g. Contribution Guide, Module READMEs, Wiki Docs etc.)
• If relevant, created or updated Code Tours here

[oZakari]

/azp run validateazcloud

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