Deprecates get_url_and_token() in favor of a more complete option: load_graph_config() that returns a full DatahubClientConfig.
This change was then propagated across previous usages of get_url_and_token so that connections to DataHub server from the client respect the full breadth of configuration specified by DatahubClientConfig.
I.e: You can now specify disable_ssl_verification: true in your ~/.datahubenv file so that all cli functions to the server work when ssl certification is disabled.
Fixes#9705
