Simplify the interface for host_callback.id_tap (#4101)
* Simplify the internal interface for host_callback.id_tap
This is a breaking change for `id_tap` users (but not `id_print` users).
This makes it easier to use (and type check) ``tap_func``, because the
expected signature is now ``tap_func(arg, transforms)`` vs
``tap_func(arg, *, transforms, **kwargs)``.
Most of the test changes are just adding whitespace/indentation, but I've
also slightly changed the way transformations are printed.
