form.field.ComboBox: does not hide the picker in case editable is false and opening it via a trigger click

@ExtAnimal

we have an override for onPickerTriggerClick() which does not honor the editable config.

inside form.field.Picker, we do have onInputClick(), which triggers togglePicker().

so, when editable is set to false, at first doFilter() gets called and then togglePicker(). it is a bit weird: after the show() call, a hide() call follows in real time. while i can not tell why the picker is not getting hidden right away, the hidden config does get changed to true. the result is that later hide() calls no longer work.

to fix this, i will just override togglePicker() to honor doFilter() and remove the onPickerTriggerClick() override. then editable true and false will both work again.