Set avoid_class_mutation to True everywhere

## Question

I came across the `avoid_class_mutation` kwarg in the definition of `_make_configurable`.

When would it be best to use one or the other option?

This parameter is also not exposed to the register and configurable decorators and has different defaults there (True for register, False for configurable). Is there a reason for it? Maybe it'd be good to expose it at least give the choice to the user ?

Thanks