tiling: Update UI on shift key press/release

Currently when dragging a window, if you stop moving the mouse (but keep the left button held down) then press/release shift, the custom tiling UI is not toggled until the mouse is moved again.

This happens because the custom tiling UI is toggled in Window::updateInteractiveMoveResize, which isn't called on key press/release (except in wayland where it's called on key press).

This MR calls updateInteractiveMoveResize on key press/release. This correctly toggles the custom tiling UI when the shift key is pressed/released without the mouse moving, and also normalises x11/wayland behaviour.

I haven't added tests as the updated methods don't appear to be tested currently so I wasn't sure how best to add them.