ST6RI-780: Nested inherited features are not correctly rendered (PlantUML)

[himi]

When the visualizer renders a connector, it also renders inherited features referred by the connector. However, it may fail to render nested features. In the example below:

package TestInheritedPart2 {
    part def Vehicle {
        part powerTrain {
            part shaft {
                port rotation;
            }
        }
    }

    part vehicle : Vehicle {
        part :>> powerTrain {
            part motor {
                part shaft {
                    port rotation;
                }
            }
            bind motor.shaft.rotation = shaft.rotation;
        }
    }
}

rendering just part vehicle gives: which lacks vehicle.powerTrain.shaft.rotation even though it is referred to by the binding connector.

This PR also fixes VSSRMember.isRedefining() by using FeatureUtil.

[himi]

After this fix, the example above is correctly rendered as: