feat(nodes): change intermediates handling

- `ImageType` is now restricted to `results` and `uploads`.
- Add a reserved `meta` field to nodes to hold the `is_intermediate` boolean. We can extend it in the future to support other node `meta`.
- Add a `is_intermediate` column to the `images` table to hold this. (When `latents`, `conditioning` etc are added to the DB, they will also have this column.)
- All nodes default to `*not* intermediate`. Nodes must explicitly be marked `intermediate` for their outputs to be `intermediate`.
- When building a graph, you can set `node.meta.is_intermediate=True` and it will be handled as an intermediate.
- Add a new `update()` method to the `ImageService`, and a route to call it. Updates have a strict model, currently only `session_id` and `image_category` may be updated.
- Add a new `update()` method to the `ImageRecordStorageService` to update the image record using the model.

invokeai/app/invocations/latent.py

@@ -370,6 +370,7 @@ class LatentsToImageInvocation(BaseInvocation):
                 image_category=ImageCategory.GENERAL,
                 session_id=context.graph_execution_state_id,
                 node_id=self.id,
+                is_intermediate=self.meta.is_intermediate
             )
 
             return ImageOutput(