ARM, test case for CheckNameAvailability operations

[XiaofeiCao]

doc: https://azure.github.io/typespec-azure/docs/howtos/ARM/resource-operations#check-name-operations

• Global Name Availability Check
  • example: https://github.com/Azure/azure-rest-api-specs/blob/db63bea839f5648462c94e685d5cc96f8e8b38ba/specification/playwrighttesting/PlaywrightTesting.Management/main.tsp#L94
  • add in https://github.com/Azure/cadl-ranch/blob/main/packages/cadl-ranch-specs/http/azure/resource-manager/models/resources/toplevel.tsp#L44
• Local Name Availability Check
  • example: https://github.com/Azure/azure-rest-api-specs/blob/9ed770a85a2cf6101e0838ceccef767ac5fdd1cc/specification/fabric/Microsoft.Fabric.Management/capacity.tsp#L53
  • add in https://github.com/Azure/cadl-ranch/blob/main/packages/cadl-ranch-specs/http/azure/resource-manager/models/resources/toplevel.tsp#L44