Add 'amd-ctk gpu list' command to display GPU info

[shiv-tyagi]

Fixes #116

Summary

Adds a new amd-ctk gpu list CLI command that displays AMD GPU information including device index, UUID, and DRM device paths. This provides a first-party way to discover GPU UUIDs needed for container configurations (AMD_VISIBLE_DEVICES), replacing the previous dependency on external tools like rocm-smi or amd-smi.

Changes

• cmd/amd-ctk/gpu/gpu.go — New gpu subcommand group under amd-ctk.
• cmd/amd-ctk/gpu/list/list.go — Implements amd-ctk gpu list. Discovers GPUs via internal/amdgpu, maps KFD topology UUIDs to device indices, and prints a formatted table of GPU Id, UUID (0x hex), and render device paths.
• cmd/amd-ctk/main.go — Registers the new gpu command.
• README.md — Replaces rocm-smi/amd-smi UUID discovery instructions with amd-ctk gpu list. Adds a note clarifying UUID source (KFD topology) vs ASIC_SERIAL/Unique ID from other tools.

Testing

Validated on an Ubuntu machine with 1 AMD GPU and the amd Docker runtime configured:

• amd-ctk --help lists the new gpu command
• amd-ctk gpu --help lists the list subcommand
• amd-ctk gpu list exits with code 0
• Output reports GPU count (Found 1 AMD GPU device)
• Output contains table headers (GPU Id, UUID, DRM Devices)
• Output shows renderD device paths
• Output shows UUID in hex format (0xD8D3E250FF726FB0)
• UUID from gpu list works with AMD_VISIBLE_DEVICES=<UUID> for container GPU injection
• Render device reported by gpu list matches the device injected into the container