feat(diffusers): various enhancements

[mudler]

Description

This PR now allows stable-diffusion2.1 and similar as well:

# https://huggingface.co/stabilityai/stable-diffusion-2-1
name: sd-2.1
parameters:
  model: stabilityai/stable-diffusion-2-1
backend: diffusers

# Force CPU usage
f16: false
diffusers:
  pipeline_type: StableDiffusionPipeline
  cuda: false
  enable_parameters: "none" # This disables all parameters except the prompt
  scheduler_type: DPMSolverMultistepScheduler

It also allows loading from file, consider:

name: sd-custom
parameters:
  model: model.safetensors # relative to /models, an URL or an absolute path
backend: diffusers

# Force CPU usage
f16: false
diffusers:
  pipeline_type: StableDiffusionPipeline
  cuda: false
  enable_parameters: "negative_prompt" # Enables negative_prompts

Notes for Reviewers

It also disable safe checks as it was getting in the way of testing - I did throw away few cycles for annoying false positives.