Generalize and simplify 'triggered when stowed test`

The `PROBE_IS_TRIGGERED_WHEN_STOWED_TEST` is able to detect if a probe is
successfully deployed/stowed.
It was part of the Allen Key probes code only.
Now the function is generally available.

Currently this test is compulsory for Allen Key probes to not alter the used behaviour
If you want to add the test for an other type of probe simply add
```
#define PROBE_IS_TRIGGERED_WHEN_STOWED_TEST
```
to your config.

Marlin/Conditionals.h

@@ -753,6 +753,10 @@
 
   #define HAS_BED_PROBE (PROBE_SELECTED && PROBE_PIN_CONFIGURED)
 
+  #if ENABLED(Z_PROBE_ALLEN_KEY)
+    #define PROBE_IS_TRIGGERED_WHEN_STOWED_TEST
+  #endif
+
   /**
    * Bed Probe dependencies
    */

Marlin/Marlin_main.cpp

@@ -1955,6 +1955,15 @@ static void clean_up_after_endstop_or_probe_move() {
 
 #if HAS_BED_PROBE
 
+ // TRIGGERED_WHEN_STOWED_TEST can easily be extended to servo probes, ... if needed.
+  #if ENABLED(PROBE_IS_TRIGGERED_WHEN_STOWED_TEST)
+    #if ENABLED(Z_MIN_PROBE_ENDSTOP)
+      #define _TRIGGERED_WHEN_STOWED_TEST (READ(Z_MIN_PROBE_PIN) != Z_MIN_PROBE_ENDSTOP_INVERTING)
+    #else
+      #define _TRIGGERED_WHEN_STOWED_TEST (READ(Z_MIN_PIN) != Z_MIN_ENDSTOP_INVERTING)
+    #endif
+  #endif
+
   static void deploy_z_probe() {
 
     #if ENABLED(DEBUG_LEVELING_FEATURE)
@@ -1966,6 +1975,14 @@ static void clean_up_after_endstop_or_probe_move() {
     // Make room for probe
     do_probe_raise(_Z_RAISE_PROBE_DEPLOY_STOW);
 
+    #ifdef _TRIGGERED_WHEN_STOWED_TEST
+      // If endstop is already false, the Z probe is deployed
+      if (_TRIGGERED_WHEN_STOWED_TEST) { // closed after the probe specific actions.
+                                        // Would a goto be less ugly?
+      //while (!_TRIGGERED_WHEN_STOWED_TEST) { idle(); // would offer the opportunity
+      // for a triggered when stowed manual probe.
+    #endif
+
     #if ENABLED(Z_PROBE_SLED)
 
       dock_sled(false);
@@ -1976,42 +1993,26 @@ static void clean_up_after_endstop_or_probe_move() {
       DEPLOY_Z_SERVO();
 
     #elif ENABLED(Z_PROBE_ALLEN_KEY)
-      float old_feedrate = feedrate;
 
-      feedrate = Z_PROBE_ALLEN_KEY_DEPLOY_1_FEEDRATE;
-
-      // If endstop is already false, the Z probe is deployed
-      #if ENABLED(Z_MIN_PROBE_ENDSTOP)
-        bool z_probe_endstop = (READ(Z_MIN_PROBE_PIN) != Z_MIN_PROBE_ENDSTOP_INVERTING);
-        if (z_probe_endstop)
-      #else
-        bool z_min_endstop = (READ(Z_MIN_PIN) != Z_MIN_ENDSTOP_INVERTING);
-        if (z_min_endstop)
-      #endif
-        {
       run_deploy_moves_script();
-        }
 
-      #if ENABLED(Z_MIN_PROBE_ENDSTOP)
-        z_probe_endstop = (READ(Z_MIN_PROBE_PIN) != Z_MIN_PROBE_ENDSTOP_INVERTING);
-        if (z_probe_endstop)
     #else
-        z_min_endstop = (READ(Z_MIN_PIN) != Z_MIN_ENDSTOP_INVERTING);
+
-        if (z_min_endstop)
+      // Nothing to be done. Just enable_z_probe below...
+
     #endif
-        {
+
+    #ifdef _TRIGGERED_WHEN_STOWED_TEST
+      }; // opened before the probe specific actions
+
+      if (_TRIGGERED_WHEN_STOWED_TEST) {
         if (IsRunning()) {
           SERIAL_ERROR_START;
-            SERIAL_ERRORLNPGM("Z-Probe failed to engage!");
+          SERIAL_ERRORLNPGM("Z-Probe failed");
           LCD_ALERTMESSAGEPGM("Err: ZPROBE");
         }
         stop();
       }
-
-    #else
-
-      // Nothing to be done. Just enable_z_probe below...
-
     #endif
 
     endstops.enable_z_probe();
@@ -2027,6 +2028,13 @@ static void clean_up_after_endstop_or_probe_move() {
     // Make more room for the servo
     do_probe_raise(_Z_RAISE_PROBE_DEPLOY_STOW);
 
+    #ifdef _TRIGGERED_WHEN_STOWED_TEST
+      // If endstop is already false, the Z probe is deployed
+      if (!_TRIGGERED_WHEN_STOWED_TEST) { // closed after the probe specific actions.
+                                        // Would a goto be less ugly?
+      //while (!_TRIGGERED_WHEN_STOWED_TEST) { idle(); // would offer the opportunity
+      // for a triggered when stowed manual probe.
+
       #if ENABLED(Z_PROBE_SLED)
 
       dock_sled(true);
@@ -2040,26 +2048,23 @@ static void clean_up_after_endstop_or_probe_move() {
 
       run_stow_moves_script();
 
-      #if ENABLED(Z_MIN_PROBE_ENDSTOP)
-        bool z_probe_endstop = (READ(Z_MIN_PROBE_PIN) != Z_MIN_PROBE_ENDSTOP_INVERTING);
-        if (!z_probe_endstop)
     #else
-        bool z_min_endstop = (READ(Z_MIN_PIN) != Z_MIN_ENDSTOP_INVERTING);
+
-        if (!z_min_endstop)
+      // Nothing to do here. Just clear endstops.z_probe_enabled
+
     #endif
-        {
+
+    #ifdef _TRIGGERED_WHEN_STOWED_TEST
+      }; // opened before the probe specific actions
+      if (!_TRIGGERED_WHEN_STOWED_TEST) {
         if (IsRunning()) {
           SERIAL_ERROR_START;
-            SERIAL_ERRORLNPGM("Z-Probe failed to retract!");
+          SERIAL_ERRORLNPGM("Z-Probe failed!");
           LCD_ALERTMESSAGEPGM("Err: ZPROBE");
         }
         stop();
+        return true;
       }
-
-    #else
-
-      // Nothing to do here. Just clear endstops.z_probe_enabled
-
     #endif
 
     endstops.enable_z_probe(false);