Our ECS Task Stop alarm wasn't going off in previous instances of our identity service failing. This diff addresses this problem by not filtering based on ecs event rules directly, but redirecting them
to a cloudwatch log group and filtering on them there.

This addresses https://linear.app/comm/issue/ENG-8847/investigate-why-alarms-dont-trigger-when-identity-service-ooms and https://linear.app/comm/issue/ENG-8156/investigate-why-ecs-task-change-didnt-trigger

Created a identity service copy on staging, reduced memory allocation and downgraded the image, and then proceeded to call GetDeviceListForUsers with ~12,000 userIDs, causing an OOM error and the task to fail.

The alarm successfully triggered and sent an email