fixes to env parsing, textual inversion & help text

- Make environment variable settings case InSenSiTive:
  INVOKEAI_MAX_LOADED_MODELS and InvokeAI_Max_Loaded_Models
  environment variables will both set `max_loaded_models`

- Updated realesrgan to use new config system.

- Updated textual_inversion_training to use new config system.

- Discovered a race condition when InvokeAIAppConfig is created
  at module load time, which makes it impossible to customize
  or replace the help message produced with --help on the command
  line. To fix this, moved all instances of get_invokeai_config()
  from module load time to object initialization time. Makes code
  cleaner, too.

- Added `--from_file` argument to `invokeai-node-cli` and changed
  github action to match. CI tests will hopefully work now.

invokeai/backend/image_util/patchmatch.py

@@ -8,8 +8,6 @@ import numpy as np
 import invokeai.backend.util.logging as logger
 from invokeai.app.services.config import get_invokeai_config
 
-config = get_invokeai_config()
-
 class PatchMatch:
     """
     Thin class wrapper around the patchmatch function.
@@ -23,6 +21,7 @@ class PatchMatch:
 
     @classmethod
     def _load_patch_match(self):
+        config = get_invokeai_config()
         if self.tried_load:
             return
         if config.try_patchmatch: