Sketcher: Handling of ESC keypress during handler execution

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Instead of terminating the handler, as mandated before this PR by ViewProviderSketch, ViewProviderSketch
delegates the action to DrawSketchHandler.

DrawSketchHandler implements by default this terminating behaviour, but allows to override it.

DrawSketchDefaultHandler (and all tools deriving from it) implement as default behaviour to cancel if
in initial state, otherwise to reset.

src/Mod/Sketcher/Gui/ViewProviderSketch.cpp

@@ -690,8 +690,7 @@ bool ViewProviderSketch::keyPressed(bool pressed, int key)
         case SoKeyboardEvent::ESCAPE: {
             // make the handler quit but not the edit mode
             if (isInEditMode() && sketchHandler) {
-                if (!pressed)
-                    sketchHandler->quit();
+                sketchHandler->registerPressedKey(pressed, key); // delegate
                 return true;
             }
             if (isInEditMode() && !drag.DragConstraintSet.empty()) {