Colocate tasks (#402)

Enables co-locating multiple tasks in a given work-set.

Tasks are bucketed by the following:
* OS
* job id
* setup container
* VM SKU & image (used in pre-1.0 style tasks)
* pool name (used in 1.0+ style tasks)
* if the task needs rebooting after the task setup script executes.

Additionally, a task will end up in a unique bucket if any of the following are true:
* The task is set to run on more than one VM
* The task is missing the `task.config.colocate` flag (all tasks created prior to this functionality) or the value is False

This updates the libfuzzer template to make use of colocation.  Users can specify co-locating all of the tasks *or* co-locating the secondary tasks.

src/api-service/__app__/onefuzzlib/agent_events.py

@@ -130,6 +130,7 @@ def on_state_update(
         # if tasks are running on the node when it reports as Done
         # those are stopped early
         node.mark_tasks_stopped_early()
+        node.to_reimage(done=True)
 
         # Model-validated.
         #
@@ -242,7 +243,6 @@ def on_worker_event_done(machine_id: UUID, event: WorkerDoneEvent) -> Result[Non
             node.debug_keep_node = True
             node.save()
 
-    node.to_reimage(done=True)
     task_event = TaskEvent(
         task_id=task.task_id, machine_id=machine_id, event_data=WorkerEvent(done=event)
     )