feat: metadata refactor

- Refactor how metadata is handled to support a user-defined metadata in graphs
- Update workflow embed handling
- Update UI to work with these changes
- Update tests to support metadata/workflow changes

invokeai/app/api_app.py

@@ -44,8 +44,8 @@ if True:  # hack to make flake8 happy with imports coming after setting up the c
         boards,
         images,
         models,
-        sessions,
         session_queue,
+        sessions,
         utilities,
         workflows,
     )