CollisionTest criteria json does not include information about the collision traffic event.

[paulbourelly999]

Describe our question or idea
Using the metrics module in scenario runner, I set up a scenario with a CollisionTest criteria. The expectation being that the metrics module would create a criteria json file indicating that a given run failed the collision test criteria along with information about the collisions or traffic events that caused it to fail. Instead I get the following json
"CollisionTest": { "children": [], "feedback_message": "", "blackbox_level": 4, "_terminate_on_failure": false, "test_status": "FAILURE", "expected_value_success": 0, "expected_value_acceptable": null, "actual_value": 1, "optional": false, "_collision_sensor": null, "other_actor": null, "other_actor_type": null, "registered_collisions": [], "last_id": null, "collision_time": 27.05000040307641, "terminate_on_failure": false },
Expected behavior
Looking through the code, the CollisionTest criteria should populate other attributes here including a collection of traffic events. While it seems to have recognized a collision took place based on the collision_time and failure state, but it seems to have not recorded any information about the collision.

Looking at the code, it seems to skip over any attributes it fails to serialize as JSON strings.

scenario_runner/scenario_runner.py

Lines 297 to 302 in d12d8bb

	try:
	key_dict = {key: criterion_dict[key]}
	json.dump(key_dict, fp, sort_keys=False, indent=4)
	criteria_dict[criterion.name].update(key_dict)
	except TypeError:
	pass

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Desktop (please complete the following information):

• OS: Ubuntu 18:04 (Docker)
• CARLA Version : 0.9.10
• Python version :3.6
• Version 0.9.10
  Note: We are currently unable to upgrade to any newer version of CARLA due to the cost of integration incurred for updating. Would prefer solutions that do not require an update.