Miscellaneous LCD code renaming, reordering (#12430)

* Move special characters to language.h
* Apply some naming standards
* Clean up menu item draw functions
* Rename some Temperature methods
* UI => ExtUI

Marlin/src/libs/buzzer.cpp

@@ -64,7 +64,7 @@ void Buzzer::tick() {
     if (state.tone.frequency > 0) {
       #if ENABLED(EXTENSIBLE_UI)
         CRITICAL_SECTION_START;
-        UI::onPlayTone(state.tone.frequency, state.tone.duration);
+        ExtUI::onPlayTone(state.tone.frequency, state.tone.duration);
         CRITICAL_SECTION_END;
       #elif ENABLED(SPEAKER)
         CRITICAL_SECTION_START;