feat: move all config-related initialization to app

HF login, legacy yaml confs, and default init file are all handled during app setup.

All directories are created as they are needed by the app.

No need to check for a valid root dir - we will make it if it doesn't exist.

invokeai/app/api_app.py

@@ -233,10 +233,6 @@ def invoke_api() -> None:
             else:
                 return port
 
-    from invokeai.backend.install.check_directories import check_directories
-
-    check_directories(app_config)  # note, may exit with an exception if root not set up
-
     if app_config.dev_reload:
         try:
             import jurigged