comfyui --benchmark option

### Feature Idea

During the discussion of #10302 it would be useful if we have a standard way to benchmark performance of various usages.

Could include:
* vae encode/decode speed (for popular base model(s))
* ksampler speed (for popular base model(s))
* Upscale by model speed

Could start with sdxl & wan, Ultrasharp upscaling.

Perhaps run comfy with `--benchmark [scenarios]` and it runs the scenarios (if the models are available on the filesystem) outputting a text report.

Would be a useful tool for just trying all the different options available locally to see what performs best in addition to comparing perf across platforms & setups.

### Existing Solutions

Adhoc testing by running workflows and checking the speed

### Other

_No response_