Encapsulate common display code in a singleton (#12395)

* Encapsulate common LCD code in a singleton
* Depend more UBL code on UBL_DEVEL_DEBUGGING
  - Since most users don't need the debugging on at all times, this helps reduce the default build size for UBL by over 2K, a little closer to fitting on 128K boards.

Marlin/src/lcd/malyanlcd.cpp

@@ -417,7 +417,7 @@ void update_usb_status(const bool forceUpdate) {
  * The optimize attribute fixes a register Compile
  * error for amtel.
  */
-void lcd_update() {
+void MarlinUI::update() {
   static char inbound_buffer[MAX_CURLY_COMMAND];
 
   // First report USB status.
@@ -461,7 +461,7 @@ void lcd_update() {
  * it and translate into gcode, which then gets injected into
  * the command queue where possible.
  */
-void lcd_init() {
+void MarlinUI::init() {
   inbound_count = 0;
   LCD_SERIAL.begin(500000);
 
@@ -479,7 +479,7 @@ void lcd_init() {
 /**
  * Set an alert.
  */
-void lcd_setalertstatusPGM(PGM_P message) {
+void MarlinUI::setalertstatusPGM(PGM_P message) {
   char message_buffer[MAX_CURLY_COMMAND];
   sprintf_P(message_buffer, PSTR("{E:%s}"), message);
   write_to_lcd(message_buffer);