Core: Enable TaskDialogs to associate view (#17373)

* Core: Add possibility for task dialogs to associate a view and be able to close when associated view is closed.

* TaskImage: Use task dialog view association.

* Sketcher: Use task dialog view association. Preventing crash (https://github.com/FreeCAD/FreeCAD/issues/16702)

* EditableDatumLabel: Use QPointer to prevent crash

src/Mod/Sketcher/Gui/TaskDlgEditSketch.cpp

@@ -79,6 +79,8 @@ TaskDlgEditSketch::TaskDlgEditSketch(ViewProviderSketch* sketchView)
         std::bind(&SketcherGui::TaskDlgEditSketch::slotToolChanged, this, sp::_1));
 
     ToolSettings->setHidden(true);
+
+    associateToObject3dView(sketchView->getObject());
 }
 
 TaskDlgEditSketch::~TaskDlgEditSketch()
@@ -145,4 +147,10 @@ bool TaskDlgEditSketch::reject()
 }
 
 
+void TaskDlgEditSketch::autoClosedOnClosedView()
+{
+    // Make sure the edit mode is exited when the view is closed.
+    reject();
+}
+
 #include "moc_TaskDlgEditSketch.cpp"

src/Mod/Sketcher/Gui/TaskDlgEditSketch.h

@@ -67,6 +67,7 @@ public:
     {
         return false;
     }
+    void autoClosedOnClosedView() override;
 
     /// returns for Close and Help button
     QDialogButtonBox::StandardButtons getStandardButtons() const override