Use new input event structs in input processing

With the introduction of the wlroots backend we added new input event structs mirroring the wlroots' ones.

These may replace the old event classes we have for processing filters and spies. These old classes inherit from QInputEvents. By that they are way too complicated for what is needed and their removal fits our strategy to reduce Qt usage overall.

Event processors to replace (in filters/spies):

• move(move_event const&), replacespointerEvent(QMouseEvent*)
• button(button_event const&), replaces pointerEvent(QMouseEvent*)
• axis(axis_event const&), replaces wheelEvent(WheelEvent*)
• key(key_event const&), replaces keyEvent(QKeyEvent*) assigned to @francesco.sorr
• touch_down(touch_down_event const&), replaces touchDown(qint32, const QPointF&, quint32) assigned to @aramgrigoryan
• touch_motion(touch_motion_event const&), replaces touchMotion(qint32, const QPointF&, quint32) assigned to @aramgrigoryan
• touch_up(touch_up_event const&), replaces touchUp(qint32, quint32) assigned to @aramgrigoryan
• pinch_begin(pinch_begin_event const&), replaces pinchGestureBegin(int, quint32) assigned to @frmonteiro
• pinch_update(pinch_update_event const&), replaces pinchGestureUpdate(qreal, qreal, const QSizeF&, quint32) assigned to @frmonteiro
• pinch_end(pinch_end_event const&), replaces pinchGestureEnd(quint32) assigned to @frmonteiro
• pinch_cancel(pinch_end_event const&), replaces pinchGestureCancelled(quint32) assigned to @frmonteiro
• swipe_begin(swipe_begin_event const&), replaces swipeGestureBegin(int, quint32) assigned to @frmonteiro
• swipe_update(swipe_update_event const&), replaces swipeGestureUpdate(const QSizeF&, quint32) assigned to @frmonteiro
• swipe_end(swipe_end_event const&), replaces swipeGestureEnd(quint32) assigned to @frmonteiro
• swipe_cancel(swipe_end_event const&), replaces swipeGestureCancelled(quint32) assigned to @frmonteiro
• switch_toggle(switch_toggle_event const&), replaces switchEvent(SwitchEvent*) assigned to @frmonteiro

The following events can not yet be replaced as the backend is not yet defined, but it is likely they should be replaced as follows once we have defined the backend:

• tablet_tool_axis(tablet_tool_axis_event const&), replaces tabletToolEvent(QTabletEvent*)
• tablet_tool_proximity(tablet_tool_proximity_event const&), replaces tabletToolEvent(QTabletEvent*)
• tablet_tool_tip(tablet_tool_tip_event const&), replaces tabletToolEvent(QTabletEvent*)
• tablet_tool_button(tablet_tool_button_event const&), replaces tabletToolButtonEvent(const QSet<uint>&)
• tablet_pad_button(tablet_pad_button_event const&), replaces tabletPadButtonEvent(const QSet<uint>&)
• tablet_pad_ring(tablet_pad_ring_event const&), replaces tabletPadRingEvent(int, int, bool)
• tablet_pad_strip(tablet_pad_strip_event const&), replaces tabletPadStripEvent(int, int, bool)