Homing backoff enhancements

- Define homing bump as an array
- Add pre and post homing backoff options
- Consolidate homing config options

Marlin/Configuration_adv.h

@@ -592,8 +592,7 @@
 
   // Default x offset in duplication mode (typically set to half print bed width)
   #define DEFAULT_DUPLICATION_X_OFFSET 100
-
-#endif // DUAL_X_CARRIAGE
+#endif
 
 // Activate a solenoid on the active extruder with M380. Disable all with M381.
 // Define SOL0_PIN, SOL1_PIN, etc., for each extruder that has a solenoid.
@@ -601,19 +600,24 @@
 
 // @section homing
 
-// Homing hits each endstop, retracts by these distances, then does a slower bump.
-#define X_HOME_BUMP_MM 5
-#define Y_HOME_BUMP_MM 5
-#define Z_HOME_BUMP_MM 2
-#define HOMING_BUMP_DIVISOR { 2, 2, 4 }  // Re-Bump Speed Divisor (Divides the Homing Feedrate)
-//#define QUICK_HOME                     // If homing includes X and Y, do a diagonal move initially
-//#define HOMING_BACKOFF_MM { 2, 2, 2 }  // (mm) Move away from the endstops after homing
+/**
+ * Homing Procedure
+ * Homing (G28) does an indefinite move towards the endstops to establish
+ * the position of the toolhead relative to the workspace.
+ */
 
-// When G28 is called, this option will make Y home before X
-//#define HOME_Y_BEFORE_X
+//#define SENSORLESS_BACKOFF_MM  { 2, 2 }     // (mm) Backoff from endstops before sensorless homing
 
-// Enable this if X or Y can't home without homing the other axis first.
-//#define CODEPENDENT_XY_HOMING
+#define HOMING_BUMP_MM      { 5, 5, 2 }       // (mm) Backoff from endstops after first bump
+#define HOMING_BUMP_DIVISOR { 2, 2, 4 }       // Re-Bump Speed Divisor (Divides the Homing Feedrate)
+
+//#define HOMING_BACKOFF_POST_MM { 2, 2, 2 }  // (mm) Backoff from endstops after homing
+
+//#define QUICK_HOME                          // If G28 contains XY do a diagonal move first
+//#define HOME_Y_BEFORE_X                     // If G28 contains XY home Y before X
+//#define CODEPENDENT_XY_HOMING               // If X/Y can't home without homing Y/X first
+
+// @section bltouch
 
 #if ENABLED(BLTOUCH)
   /**
@@ -682,6 +686,8 @@
 
 #endif // BLTOUCH
 
+// @section extras
+
 /**
  * Z Steppers Auto-Alignment
  * Add the G34 command to align multiple Z steppers using a bed probe.
@@ -2319,7 +2325,7 @@
    *    HIGHEST       255      -64    (Too sensitive => False positive)
    *    LOWEST         0        63    (Too insensitive => No trigger)
    *
-   * It is recommended to set [XYZ]_HOME_BUMP_MM to 0.
+   * It is recommended to set HOMING_BUMP_MM to { 0, 0, 0 }.
    *
    * SPI_ENDSTOPS  *** Beta feature! *** TMC2130 Only ***
    * Poll the driver through SPI to determine load when homing.