Add board MKS_BASE_HEROIC (#9924)

Followup to #9008

- Don't define micro-stepping pins for boards that lack them.
- Allow setting of 128 microsteps with `M350`.

Marlin/Conditionals_post.h

@@ -221,8 +221,12 @@
 
   // MS1 MS2 Stepper Driver Microstepping mode table
   #define MICROSTEP1 LOW,LOW
-  #define MICROSTEP2 HIGH,LOW
-  #define MICROSTEP4 LOW,HIGH
+  #if ENABLED(HEROIC_STEPPER_DRIVERS)
+    #define MICROSTEP128 LOW,HIGH
+  #else
+    #define MICROSTEP2 HIGH,LOW
+    #define MICROSTEP4 LOW,HIGH
+  #endif
   #define MICROSTEP8 HIGH,HIGH
   #define MICROSTEP16 HIGH,HIGH