Invert vertical slider direction

[DataTriny]

Closes #9932

[ogoffart]

Thanks for this PR.

I had a quick try, but the interaction with the mouse is now reversed.

[ogoffart]

Ah, it's only the Qt style that has it reverse, all the other styles are behaving properly.

[ogoffart]

So the bug with the Qt slider is that this PR doesn't actually invert it.
The same as this should be done: https://github.com/qt/qtbase/blob/6667d4998546367e0bac972617231a1ca06ee4db/src/widgets/widgets/qslider.cpp#L114

That is, in initQSliderOptions , we should set option.upsideDown = vertical;

[DataTriny]

I have applied the requested changes and removed changes to Home/End keys that were actually wrong.

However I have manually tested the Qt style and it doesn't seem to make any difference. On my Windows system, dragging the mouse towards the top increases the value and dragging it towards the bottom decreases it, as for the other styles. I tried running the test cases but I can't get the Rust driver to run the tests for Qt even though my Qt installation is working.