[WIP][Feat] platform auto detection

[Alcanderian]

Motivation

Continuous of #4928
For issue #4353

Modifications

The key difference from vLLM is multi-platform compatibility: our solution can possibly work across different platforms (e.g., CPU/GPU) in one environment, whereas vLLM is restricted to specific setups.

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 and Accuracy Results.
• For reviewers: If you haven't made any contributions to this PR and are only assisting with merging the main branch, please remove yourself as a co-author when merging the PR.
• Please feel free to join our Slack channel at https://slack.sglang.ai to discuss your PR.

[Alcanderian]

This folder will become the largest folder if the abstraction is keep going on. Hence it is not a good choice to concentrated platform code here