Use debug instead of error log for skipped events for internal task/container

[yinyic]

Summary

For internal tasks (e.g. service connect relay) or internal containers (e.g. pause containers), we do not wish to publish any state change events for them. Currently we log an error message when we encounter such task/container while constructing the events. But that could be noisy and misleading since this is not a real error but rather designed behavior. This PR updates all such error messages to be debug messages.

Implementation details

Created new error type ErrShouldNotSendEvent. This error will be returned for internal task/containers when constructing a state change event. Caller will discern this error, and log a debug instead of error message in that case.

Testing

• Ran make test
• Tested updated ECS Agent with service connect task, observed debug logs below

level=debug time=2023-02-06T21:01:52Z msg="Should not send events for internal tasks or containers: ~internal~ecs~pause-server"
level=debug time=2023-02-06T21:01:52Z msg="Should not send events for internal tasks or containers: ~internal~ecs~pause-ecs-service-connect-ciCxr"
level=debug time=2023-02-06T21:01:52Z msg="Should not send events for internal tasks or containers: instance-service-connect-relay"

New tests cover the changes: no

Description for the changelog

Use debug instead of error log for skipped events for internal task/container

Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.