Implement Implicit Parameters using `SpecialPred`

This task is a spin-off of #20897 (comment 400618). There we are discussing a change to the implementation of single-method classes (with a uniformly lifted dictionary, instead of using newtypes). For implicit argument (and hence HasCallStack) we don’t want to change the behavior here, and Simon PJ suggested to change the implementation of implicit parameters to use the SpecialPred machinery.

This would replace the current implementation, via a IP type class.