Sagemaker-training

* bug-fix: correctly set NGINX_PROXY_READ_TIMEOUT to match model_sever_timeout.
* enhancement: remove numpy version restriction.

* bug-fix: Fix recursive directory navigation in intermediate output.

* bug-fix: Rename libchangehostname to gethostname to match POSIX function name

* feature: C extension reads hostname from resourceconfig instead of env var.

* feature: Generic OpenMPI support
* bug-fix: Fix response content_type handling

* bug-fix: Accept header ANY ('*/*') fallback to default accept
* feature: Add intermediate output to S3 during training
* bug-fix: reintroduce ``_modules.s3_download`` and ``_modules.download_and_install`` for backward compatibility