UI font fallbacks: allow using more "Noto Sans xyz" (#8722)

Add a submenu allowing users to add Noto Sans fonts
to be used as UI fallback fonts.
Lots of them are alrady there on Android, but can be
downloaded (manually) and side-loaded by the user
on other platforms.

frontend/ui/elements/reader_menu_order.lua

@@ -84,6 +84,8 @@ local order = {
     },
     device = {
         "keyboard_layout",
+        "font_ui_fallbacks",
+        "----------------------------",
         "time",
         "device_status_alarm",
         "charging_led", -- if Device:canToggleChargingLED()