prevent total webui crash

rework extensions metadata: use custom sorter that doesn't mess the order as much and ignores cyclic errors, use classes with named fields instead of dictionaries, eliminate some duplicated code

add new callback for scripts to be used before processing

add a way for scripts to register a callback for before/after just a single component's creation

add VAE from main model into infotext, not from refiner model
option to make scripts UI without gr.Group
fix inconsistencies with refiner when usings samplers that do more denoising than steps

Add postprocess_batch_list script callback

typo fix

split some code from ui.py into ui_settings.py ui_gradio_edxtensions.py
add before_process callback for scripts
add ability for alwayson scripts to specify section and let user reorder those sections