[devcontainer] Fix mount and GPU & Support rust dev

[ByronHsu]

Motivation

1. The current workspaceFolder in dev container is wrong. We should just remove it and use the default setting.

Reason: The local workspace is mounted to /workspace/sglang but vscode will open /sgl-workspace/sglang/, which is actually the pre-installed sglang from the base image instead of the local one/

2. Install uv for faster dev installation and rust for rust development

3. Add --gpus=all for the container to access GPUs

Modifications

Checklist

• Format your code according to the Code Formatting with Pre-Commit.
• Add unit tests as outlined in the Running Unit Tests.
• Update documentation / docstrings / example tutorials as needed, according to Writing Documentation.
• Provide throughput / latency benchmark results and accuracy evaluation results as needed, according to Benchmark and Profiling.

[ByronHsu]

cc @zhyncs

[zhyncs]

ref https://github.com/sgl-project/sglang/actions/runs/12851850493
fix #2745