Missing tablet cursor. Set tablet cursor on Wayland with zwp_tablet_tool.set_cursor

Hello! As you all know, Wayland handles cursors client-side. Wayland's tablet input protocol, tablet-unstable-v2, expects a cursor icon to be set with the zwp_tablet_tool_v2:request:set_cursor call. This is considered a core part of the protocol.

Qt does not seem to call `set_cursor` at all. This cursor is seperate from the regular "pointer" cursor that is mouse and touchpad. So for client-cursors only compositor (i.e Weston and Mutter, although Mutter looks to land server-side cursors soon), this is absolutely needed.

From a GNOME bug ticket

From what I've seen, Qt is handling the `zwp_tablet_v2` protocol, it's just consistently forgetting to set a stylus cursor. This is not an optional aspect of the protocol, like it is not in the core Wayland protocol with `wl_pointer.set_cursor`. This kind of spec breaks would get the proper treatment in GTK, I trust Qt will also consider it important to run correctly on Wayland regardless of the compositor.