[Feature Request]: Make "Karras schedule" as an setting section for sampler

[KohakuBlueleaf]

Is there an existing issue for this?

• I have searched the existing issues and checked the recent builds/commits

What would your feature do ?

For now, we have lot of sampler from k_diffusion that has an "karras" variation which use karras schedule for the sigmas.

But, as mentioned by @Birch-san on twitter, the source code on k_diffusion and the previous issue about sigmas setting for karras scheduler. It is clear that karras scheduler should not be a "boolean" option.
(Also, some paper has said that let timestep=T has snr=0 is better than what SD have now. and snr=0 is sigma_max=inf, so let user to set sigma_max max may be a good idea)

So I am considering something like: make karras scheduler as a option like hires fix, when you enable it you will get some extra setting (slider or number input) for it.

Or we can even expand this idea to: let user choose different type of sigmas scheduler and control the parameters for them.

Proposed workflow

1. there will be an checkbox aside hires fix.
2. enable the checkbox and will toggle karras schedule
3. you can set sigma_min/sigma_max/rho for karras schedule

additional:
make a dropdown for choosing different sigma schedule

Additional information

ref:
Elucidating the Design Space of Diffusion-Based Generative Models
Common Diffusion Noise Schedules and Sample Steps are Flawed

If I have enough time I will try to impl it first and make a PR for it.

[KohakuBlueleaf]

Prototyping.

[KohakuBlueleaf]

The difference between different sigma max is huge may because the CompVisEPSDenoiser will automatically change sigma to T by the alpha schedule
And use large sigma max may need the fixed alpha schedule specified in Common Diffusion Noise Schedules and Sample Steps are Flawed