[ECS] [Cloudwatch]: Propagate tags to cloudwatch stream

With the release of https://github.com/aws/containers-roadmap/issues/15 now we can tag ecs services and tasks. It would be great if these tags are propagated to cloudwatch event stream [https://docs.aws.amazon.com/AmazonECS/latest/developerguide/ecs_cwe_events.html].

Our use case is that we have certain MonitoringDomains we plan to put these MonitoringDomain as tags in ecs services. These tags are then used for automatic routing of alerts to correct destinations.

Start with the ECS tagging context in the linked roadmap issue and the ECS CloudWatch Events documentation. Determine how ECS service and task tags should appear in the event stream, including the MonitoringDomain use case. Done means the agreed tag data is propagated consistently and documented or demonstrated in the relevant event payload.

Written by the indexing model from the issue text.