Handle more flags in print and len functions

The font::len function now handles the printing scale, so it can
immediately return the scaled length instead of having the caller
calculate it. The print function now handles CJK low/high flags and
vertically centers CJK text by default (instead of letting it stick
out on the bottom).

desktop_version/src/Font.h

@@ -63,7 +63,7 @@ struct Font
 struct PrintFlags
 {
     uint8_t scale;
-    uint8_t font_sel;
+    Font* font_sel;
     uint8_t alpha;
     uint8_t colorglyph_bri;
     bool border;