Refactor: Change RigGridBase::cellCornerVertices to return std::array

Refactored RigGridBase::cellCornerVertices to return std::array<cvf::Vec3d, 8> by value instead of taking a reference to std::array as an output parameter. This change improves code readability and leverages modern C++ return value optimizations.

Updated all call sites across the codebase to reflect the new function signature.

ApplicationLibCode/ReservoirDataModel/Well/RigGeoMechWellLogExtractor.cpp

@@ -1139,7 +1139,6 @@ void RigGeoMechWellLogExtractor::calculateIntersection()
 
         std::vector<size_t> closeCells = findCloseCells( bb );
 
-        cvf::Vec3d hexCorners[8];
         for ( size_t ccIdx = 0; ccIdx < closeCells.size(); ++ccIdx )
         {
             RigElementType elmType = femPart->elementType( closeCells[ccIdx] );
@@ -1147,6 +1146,8 @@ void RigGeoMechWellLogExtractor::calculateIntersection()
 
             const int* cornerIndices = femPart->connectivities( closeCells[ccIdx] );
 
+            std::array<cvf::Vec3d, 8> hexCorners;
+
             hexCorners[0] = cvf::Vec3d( nodeCoords[cornerIndices[0]] );
             hexCorners[1] = cvf::Vec3d( nodeCoords[cornerIndices[1]] );
             hexCorners[2] = cvf::Vec3d( nodeCoords[cornerIndices[2]] );