Fix recent Cairo xsettings changes

Fix recent Cairo xsettings changes

* lisp/dynamic-setting.el (font-setting-change-default-font):
Instead of setting the font frame parameter, just clear the font
and face cache and redraw the display.  This will re-open all
fonts as well.
* src/ftcrfont.c (ftcrfont_get_default_font_options): New
function.
* src/ftfont.h: Export.
* src/xsettings.c (apply_xft_settings): Call that function to
obtain the default font settings on Cairo.  (bug#58912,
bug#59283, bug#59271)