GeoMech Intersection updates: support multiple parts (#8160)

* Rearrange intersection classes, split single file into one-per-class

* Support multi-part geomech case intersections

ApplicationLibCode/ModelVisualization/Intersections/RivIntersectionGeometryGeneratorInterface.h

@@ -0,0 +1,34 @@
+/////////////////////////////////////////////////////////////////////////////////
+//
+//  Copyright (C) 2021 - Equinor ASA
+//
+//  ResInsight is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation, either version 3 of the License, or
+//  (at your option) any later version.
+//
+//  ResInsight is distributed in the hope that it will be useful, but WITHOUT ANY
+//  WARRANTY; without even the implied warranty of MERCHANTABILITY or
+//  FITNESS FOR A PARTICULAR PURPOSE.
+//
+//  See the GNU General Public License at <http://www.gnu.org/licenses/gpl.html>
+//  for more details.
+//
+/////////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+#include "RivIntersectionVertexWeights.h"
+
+#include "cvfArray.h"
+
+#include <vector>
+
+class RivIntersectionGeometryGeneratorInterface
+{
+public:
+    virtual bool                                             isAnyGeometryPresent() const                       = 0;
+    virtual const std::vector<size_t>&                       triangleToCellIndex() const                        = 0;
+    virtual const std::vector<RivIntersectionVertexWeights>& triangleVxToCellCornerInterpolationWeights() const = 0;
+    virtual const cvf::Vec3fArray*                           triangleVxes() const                               = 0;
+};