repo: Handle GioUnix/GioWin32 types being returned from Gio methods
It may happen that a Gio method (such as Gio.Subprocess.get_stdout_pipe()) returns an object from GioUnix. We need to handle that case in four places: gjs_lookup_object_prototype(), gjs_lookup_object_constructor(), gjs_lookup_interface_constructor(), and gjs_value_from_g_value_internal().
Introduce a new method gjs_lookup_gtype() that calls g_irepository_find_by_gtype() and then performs the necessary adjustments afterwards.
Closes: #610 (closed)