[Feature] Detailed Break down of time spend on Launching SGLang Diffusion

### Checklist

- [x] If this is not a feature request but a general question, please start a discussion at https://github.com/sgl-project/sglang/discussions. Otherwise, it will be closed.
- [x] Please use English. Otherwise, it will be closed.

### Motivation

Diffusion and LLM have huge differences in compute characteristics. We want to have a detailed optimization of the launch time spent on SGLang Diffusion.

In this sense, to optimize the launch time, we should have a detailed breakdown of what is actually taking time when we launch our models. Please use Qwen-Image as an example, and try to break down the time spent. Then let's see whether we shall spend our time on optimize the launching time.

### Related resources

_No response_