Part: allow reduction of Part ViewProvider tesselation resolution

Problem description
To display a shape, the ViewProvider creates a mesh of the shape data. The
resolution depends also on the two parameters "Angular Deflection" and
"Deviation" in the View properties. (The values of these parameters are also
updated for all objects when changing these settings in the Preferences
dialog).
Changing the parameters from a high value to a lower value has an immediate
effect on the displayed shape -- for example a circle will be displayed finer
with more line segments. But changing the parameter back to the higher value
(with less resolution) will keep the finer view-mesh instead of calculating a
coarser one. To get back to the coarse view, the object has to be manually
recomputed or the file re-opened.

Solution
I just set the meshing parameter AllowQualityDecrease to True. I guess that
this was not implemented before because this parameter is quite new (introduced
in OCC v7.5 in the year 2020).

src/Mod/Part/Gui/ViewProviderExt.cpp

@@ -951,7 +951,19 @@ void ViewProviderPartExt::updateVisual()
 
         // create or use the mesh on the data structure
         Standard_Real AngDeflectionRads = AngularDeflection.getValue() / 180.0 * M_PI;
+
+#if OCC_VERSION_HEX >= 0x070500
+        IMeshTools_Parameters meshParams;
+        meshParams.Deflection = deflection;
+        meshParams.Relative = Standard_False;
+        meshParams.Angle = AngDeflectionRads;
+        meshParams.InParallel = Standard_True;
+        meshParams.AllowQualityDecrease = Standard_True;
+
+        BRepMesh_IncrementalMesh(cShape, meshParams);
+#else
         BRepMesh_IncrementalMesh(cShape, deflection, Standard_False, AngDeflectionRads, Standard_True);
+#endif
 
         // We must reset the location here because the transformation data
         // are set in the placement property