The old design was apparently somehow tolerant of multiple instances of
the same mod in `SelectedMods`, but the new one is not.
Fix the test, because appending to a list of mods that was getting
modified by previous tests is generally not how tests should be
written.
To avoid further floating-point comparison bugs, remove all usages of
Bindable<{float,double}>, replacing them with their
Bindable<Float,Double> counterparts.