[2.0.x] Make MIN_PROBE_EDGE a general option (for electronic probes) (#10069)

Some probes don't work near the edges of the bed. This change promotes MIN_PROBE_EDGE to a general setting that applies to all probing functions.

Marlin/src/config/examples/FolgerTech/i3-2020/Configuration.h

@@ -730,6 +730,9 @@
 #define Y_PROBE_OFFSET_FROM_EXTRUDER -7     // Y offset: -front +behind [the nozzle]
 #define Z_PROBE_OFFSET_FROM_EXTRUDER -10.35 // Z offset: -below +above  [the nozzle]
 
+// Certain types of probes need to stay away from edges
+#define MIN_PROBE_EDGE 10
+
 // X and Y axis travel speed (mm/m) between probes
 #define XY_PROBE_SPEED 7500
 
@@ -973,8 +976,6 @@
   #define FRONT_PROBE_BED_POSITION 10
   #define BACK_PROBE_BED_POSITION 170
 
-  // The Z probe minimum outer margin (to validate G29 parameters).
-  #define MIN_PROBE_EDGE 10
 
   // Probe along the Y axis, advancing X after each column
   //#define PROBE_Y_FIRST
@@ -1016,7 +1017,7 @@
 
   //#define MESH_EDIT_GFX_OVERLAY   // Display a graphics overlay while editing the mesh
 
-  #define MESH_INSET 0              // Mesh inset margin on print area
+  #define MESH_INSET 0              // Set Mesh bounds as an inset region of the bed
   #define GRID_MAX_POINTS_X 10      // Don't use more than 15 points per axis, implementation limited.
   #define GRID_MAX_POINTS_Y 10
 
@@ -1039,7 +1040,7 @@
   //=================================== Mesh ==================================
   //===========================================================================
 
-  #define MESH_INSET 10          // Mesh inset margin on print area
+  #define MESH_INSET 10          // Set Mesh bounds as an inset region of the bed
   #define GRID_MAX_POINTS_X 3    // Don't use more than 7 points per axis, implementation limited.
   #define GRID_MAX_POINTS_Y GRID_MAX_POINTS_X