Terminal Suggest: Default executable extension filter

[Tyriar]

We talked about Windows lacking the executable bit and are just showing all extensions currently. It's already annoying me tbh, we should add a default executable files setting on Windows ([] / undefined on mac/linux) so dll, xml`, etc. don't show by default. The majority of the results at the top aren't relevant for me:

This should also improve performance a little as we won't need to create 6000 completion items.