add flux2 support

[leejet]

.\bin\Release\sd.exe --diffusion-model  ..\..\ComfyUI\models\diffusion_models\flux2-dev-Q4_K_S.gguf --vae ..\..\ComfyUI\models\vae\flux2_ae.safetensors  --llm ..\..\ComfyUI\models\text_encoders\Mistral-Small-3.2-24B-Instruct-2506-Q4_K_M.gguf -r .\kontext_input.png -p "change 'flux.cpp' to 'flux2-dev.cpp'" --cfg-scale 1.0 --sampling-method euler -v --diffusion-fa --offload-to-cpu

TODO:

• Flux2FlowDenoiser

[stduhpf]

It runs surprisingly not too slow with a Q2_K quant. Quality is pretty bad though with that quant. If someone has enough memory and disk space to make an iq3_xxs quant of this model, that would probably be a lot better quality than the Q2 while fitting in 16 GB of VRAM.