[V3] --token and --no-instance flags (#1872)

* Ability to run Red with token without instance

* --no-instance flag

* Reformatted cli with black

* Fix changes requested by @Tobotimus

- Use "system reboot" to be clearer
- save_default_config renamed to create_temp_config
- More documentation for the create_temp_config function

* Update create_temp_config call

* Fix up imports

redbot/core/cli.py

@@ -138,6 +138,16 @@ def parse_cli_flags(args):
         action="store_true",
         help="Enables the built-in RPC server. Please read the docs prior to enabling this!",
     )
+    parser.add_argument("--token", type=str, help="Run Red with the given token.")
+    parser.add_argument(
+        "--no-instance",
+        action="store_true",
+        help=(
+            "Run Red without any existing instance. "
+            "The data will be saved under a temporary folder "
+            "and deleted on next system restart."
+        ),
+    )
     parser.add_argument(
         "instance_name", nargs="?", help="Name of the bot instance created during `redbot-setup`."
     )