feat(nodes): address feedback

- Address database feedback:
  - Remove all the extraneous tables. Only an `images` table now:
  - `image_type` and `image_category` are unrestricted strings. When creating images, the provided values are checked to ensure they are a valid type and category.
  - Add `updated_at` and `deleted_at` columns. `deleted_at` is currently unused.
  - Use SQLite's built-in timestamp features to populate these. Add a trigger to update `updated_at` when the row is updated. Currently no way to update a row.
  - Rename the `id` column in `images` to `image_name`
- Rename `ImageCategory.IMAGE` to `ImageCategory.GENERAL`
- Move all exceptions outside their base classes to make them more portable.
- Add `width` and `height` columns to the database. These store the actual dimensions of the image file, whereas the metadata's `width` and `height` refer to the respective generation parameters and are nullable.
- Make `deserialize_image_record` take a `dict` instead of `sqlite3.Row`
- Improve comments throughout
- Tidy up unused code/files and some minor organisation

invokeai/app/invocations/latent.py

@@ -372,7 +372,7 @@ class LatentsToImageInvocation(BaseInvocation):
             image_dto = context.services.images_new.create(
                 image=image,
                 image_type=ImageType.RESULT,
-                image_category=ImageCategory.IMAGE,
+                image_category=ImageCategory.GENERAL,
                 session_id=context.graph_execution_state_id,
                 node_id=self.id,
             )