Update ecs-agent/ ECS model with missing fields + consume the same

[danehlim]

Summary

Update ECS model defined in ecs-agent/api/ecs/model/ with missing fields and consume the aforementioned ECS model.

The missing fields that were added can be seen in the diff introduced by this pull request to the ecs-agent/api/ecs/model/api/api-2.json file. For reference, those fields were introduced in the following previous pull requests:

• Branch remove token #1711
• add select model updates from autogenerated model #2723
• adding support for container port range [part 1] #3473

Implementation details

1. Update ECS model defined in ecs-agent/api/ecs/model/ with missing fields
   • Add missing fields to ecs-agent/api/ecs/model/api/api-2.json file
   • Run make gogenerate to re-generate the .go files in ecs-agent/api/ecs/model/ecs/
2. Consume the ECS model files defined in ecs-agent/api/ecs/model/ecs/
   • Replace imports of github.com/aws/amazon-ecs-agent/ecs-agent/ecs_client/model/ecs with github.com/aws/amazon-ecs-agent/ecs-agent/api/ecs/model/ecs
   • Remove ecs-agent/ecs_client directory and all files contained within that directory as it is no longer used

Testing

Unit, integration, and functional tests.

New tests cover the changes: no

Description for the changelog

Update ecs-agent/ ECS model with missing fields + consume the same

Licensing

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