refactor(nodes): merge processors

Consolidate graph processing logic into session processor.

With graphs as the unit of work, and the session queue distributing graphs, we no longer need the invocation queue or processor.

Instead, the session processor dequeues the next session and processes it in a simple loop, greatly simplifying the app.

- Remove `graph_execution_manager` service.
- Remove `queue` (invocation queue) service.
- Remove `processor` (invocation processor) service.
- Remove queue-related logic from `Invoker`. It now only starts and stops the services, providing them with access to other services.
- Remove unused `invocation_retrieval_error` and `session_retrieval_error` events, these are no longer needed.
- Clean up stats service now that it is less coupled to the rest of the app.
- Refactor cancellation logic - cancellations now originate from session queue (i.e. HTTP cancel endpoint) and are emitted as events. Processor gets the events and sets the canceled event. Access to this event is provided to the invocation context for e.g. the step callback.
- Remove `sessions` router; it provided access to `graph_executions` but that no longer exists.

invokeai/app/util/step_callback.py

@@ -1,9 +1,9 @@
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Callable
 
 import torch
 from PIL import Image
 
-from invokeai.app.services.invocation_processor.invocation_processor_common import CanceledException, ProgressImage
+from invokeai.app.services.session_processor.session_processor_common import CanceledException, ProgressImage
 from invokeai.backend.model_manager.config import BaseModelType
 
 from ...backend.stable_diffusion import PipelineIntermediateState
@@ -11,7 +11,6 @@ from ...backend.util.util import image_to_dataURL
 
 if TYPE_CHECKING:
     from invokeai.app.services.events.events_base import EventServiceBase
-    from invokeai.app.services.invocation_queue.invocation_queue_base import InvocationQueueABC
     from invokeai.app.services.shared.invocation_context import InvocationContextData
 
 
@@ -34,10 +33,10 @@ def stable_diffusion_step_callback(
     context_data: "InvocationContextData",
     intermediate_state: PipelineIntermediateState,
     base_model: BaseModelType,
-    invocation_queue: "InvocationQueueABC",
     events: "EventServiceBase",
+    is_canceled: Callable[[], bool],
 ) -> None:
-    if invocation_queue.is_canceled(context_data.session_id):
+    if is_canceled():
         raise CanceledException
 
     # Some schedulers report not only the noisy latents at the current timestep,