GdkWin32: implement surface's "icon_list" property setter
The 'set_icon_list' implementation of gtk+3 was somehow dropped during the early conversion of GdkWindow to GdkSurface for gtk4.
Add it again, with minor tweaks to support GdkSurface.
Add a new internal API _gdk_win32_create_hicon_for_texture()
for sharing the existing GdkTexture-to-HICON conversion with GdkCursor.
This change allows gtk_window_set_icon_name()
to work on win32 (until now the displayed icon was typically the fallback one bundled in libgtk.dll).