WaylandCursorImage::loadThemeCursor(const T &shape) uses templates.
These templates are used by input.cpp but the deifnition is in
pointer_input.cpp

On some setups this creates a compilation problem.

This patch introduces an explicit non-templated declaration with the
defintion explicitly complied into the same class.

In master this has been refactored away anyway, so this is a minimal
patch to make things working in the least invasive way.

BUG: 423052