Use the EcsRunLauncher in the reference deployment

Summary:
Unfortunately, the EcsRunLauncher doesn't support the local development
instructions becuase the local Docker containers can't use

https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task-metadata-endpoint-v4.html

to introspect information about itself. Additionally, we can't use the
AWS SDK to launch local docker containers via the ECS API.

This shouldn't be merged until https://dagster.phacility.com/D8404 lands
and is published to pypi - prior to that, containers will fail to stand up
because the EcsRunLauncher class won't exist yet.

Test Plan: manually tested

Reviewers: dgibson, johann, catherinewu

Reviewed By: dgibson

Differential Revision: https://dagster.phacility.com/D8492