ScrollPosition scale factor fix

[ickshonpe]

Objective

Scroll position uses physical coordinates. This means scrolling may go faster or slower depending on the scroll factor. Also the scrolled position will change when the scale factor changes.

Solution

In ui_layout_system convert max_possible_offset to logical coordinates before clamping the scroll position. Then convert the clamped scroll position to physical coordinates before propagating it to the node's children.

Testing

Look at the scroll example. On main if you change your display's scale factor the items displayed by the scrolling lists will change because ScrollPosition's displacement values don't respect scale factor. With this PR the displacement will be scaled too, and the won't move.