Stabilise LMS and further stabilise DPM++ to eliminate residual noise in the result

[nhnt11]

What does this PR do?

This PR makes two changes:

1. For the LMS scheduler, introduces a parameter that forces order=1 for the last 15 steps. This makes LMS usable with Image to Image with strength closer to 0 (e.g. 0.1). This solves LMS scheduler leaves a lot of noise leftover in the result image when used with SDXL Img2Img Pipeline #5630 (more example results in that issue's thread)
2. For the DPMSolverMultistep scheduler, we force the last sigma to be 0.0 if euler_at_final is true. This prevents residual noise in the result image. This solves DPM++ leaves residual noise in SDXL images, which is unexpected #5689 (more example results in that issue's thread)

Fixes #5630, #5689

[nhnt11]

I am still working on cleaning this up a bit and updating documentation for the LMS config param 🙏

[patrickvonplaten]

@yiyixuxu could you take a look here?

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint.

[patrickvonplaten]

Gentle ping here @yiyixuxu

[yiyixuxu]

hi sorry I didn't have time to look into this sooner. We got a couple more bug reports on DPM scheduler with use_karras_sigmas, so I looked into it more. I think there was an issue in our implementation with use_karras_sigmas, and you are absolutely correct that the last sigma should be 0 (that's how it is done in k-diffusions)

I'm working on fixing it with PR here #6477