[Sketcher] Add some utility functions to Sketcher::Constraint

`involvesGeoId`, `invovesGeoIdAndPosId`, `substituteIndexAndPos`

src/Mod/Sketcher/App/Constraint.cpp

@@ -239,6 +239,25 @@ void Constraint::substituteIndex(int fromGeoId, int toGeoId)
     }
 }
 
+void Constraint::substituteIndexAndPos(int fromGeoId,
+                                       PointPos fromPosId,
+                                       int toGeoId,
+                                       PointPos toPosId)
+{
+    if (this->First == fromGeoId && this->FirstPos == fromPosId) {
+        this->First = toGeoId;
+        this->FirstPos = toPosId;
+    }
+    if (this->Second == fromGeoId && this->SecondPos == fromPosId) {
+        this->Second = toGeoId;
+        this->SecondPos = toPosId;
+    }
+    if (this->Third == fromGeoId && this->ThirdPos == fromPosId) {
+        this->Third = toGeoId;
+        this->ThirdPos = toPosId;
+    }
+}
+
 std::string Constraint::typeToString(ConstraintType type)
 {
     return type2str[type];

src/Mod/Sketcher/App/Constraint.h

@@ -132,6 +132,21 @@ public:
     /// utility function to swap the index in First/Second/Third of the provided constraint from the
     /// fromGeoId GeoId to toGeoId
     void substituteIndex(int fromGeoId, int toGeoId);
+    /// utility function to swap the index and position in First/Second/Third of the provided
+    /// constraint from {fromGeoId, fromPosId} to {toGeoId, toPosId}.
+    void substituteIndexAndPos(int fromGeoId, PointPos fromPosId, int toGeoId, PointPos toPosId);
+
+    /// utility function to check if `geoId` is one of the geometries
+    bool involvesGeoId(int geoId) const
+    {
+        return First == geoId || Second == geoId || Third == geoId;
+    }
+    /// utility function to check if (`geoId`, `posId`) is one of the points/curves
+    bool involvesGeoIdAndPosId(int geoId, PointPos posId) const
+    {
+        return (First == geoId && FirstPos == posId) || (Second == geoId && SecondPos == posId)
+            || (Third == geoId && ThirdPos == posId);
+    }
 
     std::string typeToString() const
     {