[Core] adding PointLocalCoordinates and ShapeFunctionValues to triangle 3d6

[ddiezrod]

This PR adds two missing functions to Triangle3D6: ShapeFunctionValues and PointLocalCoordinates. Regarding the latter, we use the same approach we used in #11767 for the tetra. We check if the lines of the triangle are actually straight edges, and if so, we can use the same implementation that we use for triangle 3d3. To avoid code duplication I moved the actual implementation to geometry utils (again, same thing as we did for tets)

[loumalouomega]

LGTM

[AlejandroCornejo]

This PR adds two missing functions to Triangle3D6: ShapeFunctionValues and PointLocalCoordinates. Regarding the latter, we use the same approach we used in #11767 for the tetra. We check if the lines of the triangle are actually straight edges, and if so, we can use the same implementation that we use for triangle 3d3. To avoid code duplication I moved the actual implementation to geometry utils (again, same thing as we did for tets)

@atfard let's see if this helps our issue (@loumalouomega we were trying to use linar conditions like 3D3N for mesh tying of quadratic tetras)

[loumalouomega]

This PR adds two missing functions to Triangle3D6: ShapeFunctionValues and PointLocalCoordinates. Regarding the latter, we use the same approach we used in #11767 for the tetra. We check if the lines of the triangle are actually straight edges, and if so, we can use the same implementation that we use for triangle 3d3. To avoid code duplication I moved the actual implementation to geometry utils (again, same thing as we did for tets)

@atfard let's see if this helps our issue (@loumalouomega we were trying to use linar conditions like 3D3N for mesh tying of quadratic tetras)

A priori the proper quadratic implementation should be done, otherwise can give issues. Can work as initial approximation