BREAKING CHANGES: invocations now require model key, not base/type/name

- Implement new model loader and modify invocations and embeddings

- Finish implementation loaders for all models currently supported by
  InvokeAI.

- Move lora, textual_inversion, and model patching support into
  backend/embeddings.

- Restore support for model cache statistics collection (a little ugly,
  needs work).

- Fixed up invocations that load and patch models.

- Move seamless and silencewarnings utils into better location

invokeai/backend/embeddings/__init__.py

@@ -0,0 +1,4 @@
+"""Initialization file for invokeai.backend.embeddings modules."""
+
+# from .model_patcher import ModelPatcher
+# __all__ = ["ModelPatcher"]