wayland: Use cursor position in logical monitor

When using two monitors size by side with different scales, once the cursor moves from one output to another one, its size changes based on the scale of the given output.

Changing the size of the cursor can cause the cursor area to change output again if the hotspot is not exactly at the top left corner of the area, causing the texture of the cursor to change, which will trigger another output change, so on and so forth causing continuous surface enter/leave events which flood the clients and eventually kill them.

Change the logic to use only the hotspot of the cursor to determine if its on the given logical monitor, so that it remains immune to scale changes induced by output scale differences.

Closes: #83 (closed)