fix: canvas not working on queue

Add `batch_id` to outbound events. This necessitates adding it to both `InvocationContext` and `InvocationQueueItem`. This allows the canvas to receive images.

When the user enqueues a batch on the canvas, it is expected that all images from that batch are directed to the canvas.

The simplest, most flexible solution is to add the `batch_id` to the invocation context-y stuff. Then everything knows what batch it came from, and we can have the canvas pick up images associated with its list of canvas `batch_id`s.

invokeai/app/util/step_callback.py

@@ -112,6 +112,7 @@ def stable_diffusion_step_callback(
     context.services.events.emit_generator_progress(
         queue_id=context.queue_id,
         queue_item_id=context.queue_item_id,
+        queue_batch_id=context.queue_batch_id,
         graph_execution_state_id=context.graph_execution_state_id,
         node=node,
         source_node_id=source_node_id,