Rework LCD implementation to use timestamp_t

Marlin/ultralcd_impl_DOGM.h

 #include "ultralcd_st7920_u8glib_rrd.h"
 #include "Configuration.h"
 
+#include "timestamp_t.h"
+
 #if DISABLED(MAPPER_C2C3) && DISABLED(MAPPER_NON) && ENABLED(USE_BIG_EDIT_FONT)
   #undef USE_BIG_EDIT_FONT
 #endif
     }
 
     u8g.setPrintPos(80,48);
-    millis_t time = print_job_timer.duration() / 60;
-    if (time != 0) {
-      lcd_print(itostr2(time/60));
-      lcd_print(':');
-      lcd_print(itostr2(time%60));
-    }
+
+    char buffer[10];
+    timestamp_t time(print_job_timer.duration());
+    time.toString(buffer, true);
+    if (time.timestamp != 0) lcd_print(buffer);
+    else lcd_printPGM(PSTR("--:--"));
   #endif
 
   // Extruders

Marlin/ultralcd_impl_HD44780.h

 * Implementation of the LCD display routines for a Hitachi HD44780 display. These are common LCD character displays.
 **/
 
+#include "timestamp_t.h"
+
 extern volatile uint8_t buttons;  //an extended version of the last checked buttons in a bit array.
 
 ////////////////////////////////////
     lcd.setCursor(LCD_WIDTH - 6, 2);
     lcd.print(LCD_STR_CLOCK[0]);
 
-    uint16_t time = print_job_timer.duration() / 60;
-    if (time != 0) {
-      lcd.print(itostr2(time / 60));
-      lcd.print(':');
-      lcd.print(itostr2(time % 60));
-    }
-    else {
-      lcd_printPGM(PSTR("--:--"));
-    }
+    char buffer[10];
+    timestamp_t time(print_job_timer.duration());
+    time.toString(buffer, true);
+    if (time.timestamp != 0) lcd_print(buffer);
+    else lcd_printPGM(PSTR("--:--"));
 
   #endif // LCD_HEIGHT > 3