[WIP] Decouple Container Instance Health from the doctor.

[alexcmms]

Summary

This change decouples Container Instance Health from the doctor. The primary changes are:

1. The addition of the instanceStatusMessages chan to the TCS client.
2. Moving they types relevant to instance health out of the doctor to the TCS model.
3. My IDE updated comments based on the style guidelines I have configured. I can change these if they don't match the standards of the code base.

Implementation details

The instanceStatusMessages chan follows the existing pattern of for container health and metrics in the TCS client. The addition of the chan is optional when instantiating the client in order to maintain backwards compatibility.

Testing

Description for the changelog

Enhancement - Decouple Container Instance Health from the doctor.

Additional Information

Does this PR include breaking model changes? If so, Have you added transformation functions?
No

Does this PR include the addition of new environment variables in the README?
No

Licensing

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