This MR adds proper key filtering to make sure we are not missing hotkeys when a QQuickControl has the mouse focus.
When the player is hidden, keyboard navigation fully works (left, right, up, down).
When the player is visible we make sure the QML never grabs navigation keys and we forward them as hotkey(s) to the player. It means we have to use tab and backtab to navigate through the QML player controls.
