Store value generator types/factories in the the model and remove the selector

[ajcvickers]

Move away from ValueGeneratorSelector, which was born out of one-model-to-rule-them-all, and instead configure the value generator type directly in the model. This shouldn't be too difficult, but it will be a breaking change, especially for providers.

[ajcvickers]

Note: value is quite low here. But end-result would likely be less complex code.

[AndriySvyryd]

Also apply WithConverter on the stored generator consistently.