Integrate restart policy into the container object

[sparrc]

Summary

• Integrates restart policy into the Container object, with a helper function to check if the container restart policy is defined and enabled.
• Initializes the RestartTracker object when unmarshaling the task payload, if the container has a restart policy defined and enabled.
• go mod vendor in the agent/ dir to pull in ecs-agent/ shared lib changes.

Exact struct naming is still subject to change but this should roughly match the GA feature.

Testing

New tests cover the changes:

Description for the changelog

NA

Does this PR include breaking model changes? If so, Have you added transformation functions?

Licensing

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