Multiple Wrapper Mappings

[braindeaf]

Allow usage of wrapper_mapping sets whilst maintaining backwards
compatible config as per issue/suggestion
#1632

[braindeaf]

We've been using my fork in production for just over a year now :)

[ldonnet]

It could be so helpful if this PR could be merged because it could be very useful in many use cases. On my side, I want to migrate from bootstrap to tailwind with specific simple form wrappers and this PR permits to improve gem uses.
@braindeaf Thanks for your work and explanations!

[ldonnet]

@braindeaf Have you continue improvements like integrated wrapper_mapping in form ?

config.wrappers :my_special_form do |b|
  b.wrapper_mapping :my_special_mapping
  b.use :input
  # ...
end

config.wrapper_mappings[:my_special_mapping] = {
  boolean: :my_special_boolean,
  # ....
}

Then when using the form in the view like this it would know which form wrapper to use and also automatically which mapping to use for this wrapper:

simple_form_for(animal, wrapper: :my_special_form)