Merge feature ecs-anywhere-gpu support to dev

[prateekchaudhry]

Summary

This change adds the ability to handle GPU tasks for external instances. For external instances, GPU support will rely on nvidia-container-runtime package, for which the support has been added in this PR. For internal instances, the behavior is unchanged.

Implementation details

• For external instance, use DeviceRequest struct to carry GPU IDs for using nvidia-container-runtime
• For internal instance, the environment variable NVIDIA_VISIBLE_DEVICES will continue to carry GPU IDs (unchanged behavior, continue to use default runtime)

Testing

• Manually tested changes running GPU tasks on external and internal instances
• Added unit tests to verify GPU IDs are properly populated for internal and external instances.
• Verified using 'make test'

New tests cover the changes: yes

Description for the changelog

Add support for GPU tasks for external instances

Licensing

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