Add Azure Government support for KeyVault endpoint

[the3venthoriz0n]

azapi_data_plane_resource cannot hit the proper endpoint without a provider endpoint override. This adds support for Azure Government to hit the proper KeyVault endpoint without using a provider configuration.

provider "azapi" { endpoint = [{ resource_manager_audience = "https://vault.usgovcloudapi.net" # Required to hit the data plane endpoints }] }