- This is opt-in behaviour via the provider property `use_msal`, and
  environment variables `ARM_USE_MSAL` / `ARM_USE_MSGRAPH` (the latter
  for compatibility with the related backend property

- When `use_msal` is true, do not make any API calls to a graph API
  (legacy or current). There are only 2 uses of this at present:

  - `data.azurerm_client_config`, which doesn't actually do anything
    with the result so this appears to be a vestige anyway
  - `azurerm_hdinsight_kafka_cluster`, the API for which requires
    both an AAD group ID and name to be specified (?) so currently
    this resource looks up the group name from the supplied ID. In
    future we'll require that both are specified (e.g. using
    `data.azuread_group` for any necessary lookup)

- In v3.0, we'll remove support for graph clients in order to delegate
  any required usage to the AzureAD provider.

- Also removes support for Azure Germany, which is now offline

Co-authored-by: Tom Harvey <tombuildsstuff@users.noreply.github.com>

Co-authored-by: Tom Harvey <tombuildsstuff@users.noreply.github.com>