Add get_amdgpu_memory_capacity()

[HaiShaw]

Motivation

Current use of get_gpu_memory_capacity() will break build for SGLang on ROCm (since v0.3.5.post2).

Modifications

Added get_amdgpu_memory_capacity(), and rename previous function to get_nvgpu_memory_capacity()

Checklist

• [+] Format your code according to the Contributor Guide.
• [+] Add unit tests as outlined in the Contributor Guide.
• [+] Update documentation as needed, including docstrings or example tutorials.

[ByronHsu]

How was it working on AMD before?

[HaiShaw]

Worked on v0.3.5.post1 and before, code path was different.