✨ Fan tachometer support (#23086, #23180, #23199)

Co-Authored-By: Scott Lahteine <github@thinkyhead.com>

Marlin/src/gcode/gcode.cpp

@@ -65,6 +65,10 @@ GcodeSuite gcode;
   #include "../feature/password/password.h"
 #endif
 
+#if HAS_FANCHECK
+  #include "../feature/fancheck.h"
+#endif
+
 #include "../MarlinCore.h" // for idle, kill
 
 // Inactivity shutdown
@@ -296,6 +300,8 @@ void GcodeSuite::dwell(millis_t time) {
  * Process the parsed command and dispatch it to its handler
  */
 void GcodeSuite::process_parsed_command(const bool no_ok/*=false*/) {
+  TERN_(HAS_FANCHECK, fan_check.check_deferred_error());
+
   KEEPALIVE_STATE(IN_HANDLER);
 
  /**
@@ -577,6 +583,10 @@ void GcodeSuite::process_parsed_command(const bool no_ok/*=false*/) {
         case 113: M113(); break;                                  // M113: Set Host Keepalive interval
       #endif
 
+      #if HAS_FANCHECK
+        case 123: M123(); break;                                  // M123: Report fan states or set fans auto-report interval
+      #endif
+
       #if HAS_HEATED_BED
         case 140: M140(); break;                                  // M140: Set bed temperature
         case 190: M190(); break;                                  // M190: Wait for bed temperature to reach target