Change Marlin debug flag names to fix conflicts (#12340)

In reference to #11000

Marlin/src/HAL/HAL_STM32/HAL.h

 #pragma once
 
 #define CPU_32_BIT
-#undef DEBUG_NONE
 
 #ifndef vsnprintf_P
   #define vsnprintf_P vsnprintf

Marlin/src/HAL/HAL_STM32F1/HAL.h

  */
 
 #define CPU_32_BIT
-#undef DEBUG_NONE
 
 #ifndef vsnprintf_P
   #define vsnprintf_P vsnprintf
 #include <Arduino.h>
 
 // --------------------------------------------------------------------------
-// Undefine DEBUG_ settings
-// --------------------------------------------------------------------------
-
-
-#undef DEBUG_NONE
-#undef DEBUG_FAULT
-#undef DEBUG_ALL
-
-// --------------------------------------------------------------------------
 // Includes
 // --------------------------------------------------------------------------
 

Marlin/src/HAL/HAL_STM32F1/README.md

 #endif
 <>
 
-Add the following 3 lines:
-<>
-#undef DEBUG_NONE
-#undef DEBUG_FAULT
-#undef DEBUG_ALL
-<>
-
 ### Main developers:
 Victorpv
 xC000005
 
 PRs should only be sent to Marlin bugfix-2.0.x branch once tested in printing so not to introduce new bugs.
 For testing/dev, you can submit to the above branch
-
-

Marlin/src/HAL/HAL_STM32F4/HAL.h

 #pragma once
 
 #define CPU_32_BIT
-#undef DEBUG_NONE
 
 #ifndef vsnprintf_P
   #define vsnprintf_P vsnprintf

Marlin/src/HAL/HAL_STM32F7/HAL.h

 #pragma once
 
 #define CPU_32_BIT
-#undef DEBUG_NONE
 
 #ifndef vsnprintf_P
   #define vsnprintf_P vsnprintf

Marlin/src/core/serial.cpp

 
 #include "serial.h"
 
-uint8_t marlin_debug_flags = DEBUG_NONE;
+uint8_t marlin_debug_flags = MARLIN_DEBUG_NONE;
 
 const char errormagic[] PROGMEM = "Error:";
 const char echomagic[]  PROGMEM = "echo:";

Marlin/src/core/serial.h

 /**
  * Define debug bit-masks
  */
-enum DebugFlags : unsigned char {
-  DEBUG_NONE          = 0,
-  DEBUG_ECHO          = _BV(0), ///< Echo commands in order as they are processed
-  DEBUG_INFO          = _BV(1), ///< Print messages for code that has debug output
-  DEBUG_ERRORS        = _BV(2), ///< Not implemented
-  DEBUG_DRYRUN        = _BV(3), ///< Ignore temperature setting and E movement commands
-  DEBUG_COMMUNICATION = _BV(4), ///< Not implemented
-  DEBUG_LEVELING      = _BV(5), ///< Print detailed output for homing and leveling
-  DEBUG_MESH_ADJUST   = _BV(6), ///< UBL bed leveling
-  DEBUG_ALL           = 0xFF
+enum MarlinDebugFlags : uint8_t {
+  MARLIN_DEBUG_NONE          = 0,
+  MARLIN_DEBUG_ECHO          = _BV(0), ///< Echo commands in order as they are processed
+  MARLIN_DEBUG_INFO          = _BV(1), ///< Print messages for code that has debug output
+  MARLIN_DEBUG_ERRORS        = _BV(2), ///< Not implemented
+  MARLIN_DEBUG_DRYRUN        = _BV(3), ///< Ignore temperature setting and E movement commands
+  MARLIN_DEBUG_COMMUNICATION = _BV(4), ///< Not implemented
+  MARLIN_DEBUG_LEVELING      = _BV(5), ///< Print detailed output for homing and leveling
+  MARLIN_DEBUG_MESH_ADJUST   = _BV(6), ///< UBL bed leveling
+  MARLIN_DEBUG_ALL           = 0xFF
 };
 
 extern uint8_t marlin_debug_flags;
-#define DEBUGGING(F) (marlin_debug_flags & (DEBUG_## F))
+#define DEBUGGING(F) (marlin_debug_flags & (MARLIN_DEBUG_## F))
 
 #if TX_BUFFER_SIZE < 1
   #define SERIAL_FLUSHTX_P(p)

Marlin/src/gcode/bedlevel/abl/G29.cpp

   // G29 Q is also available if debugging
   #if ENABLED(DEBUG_LEVELING_FEATURE)
     const uint8_t old_debug_flags = marlin_debug_flags;
-    if (seenQ) marlin_debug_flags |= DEBUG_LEVELING;
+    if (seenQ) marlin_debug_flags |= MARLIN_DEBUG_LEVELING;
     if (DEBUGGING(LEVELING)) {
       DEBUG_POS(">>> G29", current_position);
       log_machine_info();