Add support for models hosted on platforms other than SageMaker

[aarora79]

While this tool was never thought of as testing models hosted on anything other than SageMaker, but technically there is nothing preventing this. There are two things that need to happen for this.

1/ The models have to be deployed on the platform of choice. This part can be externalized, meaning the deployment code in this repo does not deploy those models, they are deployed separately, outside of this tool.

2/ Have support for bring your own inference script which knows how to query your endpoint. This inference script then runs inferences against the endpoints on platforms other than SageMaker. And so at this point it does not matter if the endpoint is on EKS or EC2.