They were causing infinite recursion because they were calling
themselves.
Also add the missing MapModel::reset
Yet another motivation for https://github.com/slint-ui/slint/issues/3888
as the code was mixing the `reset` function on the adapter meaning
"please re-apply the adapter filter/map/sort function" with the `reset`
function on Model which means "the subclass has changed and we should
notify listeners".
Fixes#4968
This was requested by a customer recently and it seems rather straight-forward to implement and offer. `clear()` mirrors `std::vector::clear()` and `set_vector` mirrors the `set_vec` we have in Rust.
