Handle --gpus flag using CDI

[elezar]

This change switches to using CDI to handle the --gpus flag. This removes the custom implementation that invoked the nvidia-container-cli directly. This mechanism does not align with existing implementations.

See also:

• Equivalent change in ctr: https://github.com/containerd/containerd/pull/12537
• Equivalent change in docker: https://github.com/moby/moby/pull/50228

[elezar]

Yes, most likely. I will look at updating the docs too.

Update: Updated.

[ChengyuZhu6]

This PR can fix the issue https://github.com/containerd/nerdctl/issues/4621