xcb: XInput2 fixes, enter/leave event fixes

Added enter/leave event handling in XInput2 to avoid problems with
those events when the mouse is grabbed.

This commit amends: 53d289ec
This commit amends: ed2e1578



Task-number: QTBUG-50340
Change-Id: I7a120b46daa4f8fa4c218346273ae90b6abfa156
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@theqtcompany.com>