[GeoMechanicsApplication] Assessment of making TransientPwElement inherent from Element

[markelov208]

Currently, TransientPwElement is inherent from UPw element which leads to unnecessary methods. At the same time TransientPwLineElement is inherent from Element and it has much smaller number of methods.

This issue goal is to investigate making TransientPwElement inherent from Element.

[markelov208]

TransientPwElement has 27 functions, 20 of them are tested by the integration tests in test_transient_groundwater_flow.py
The following functions are tested:

1. Create(IndexType NewId, NodesArrayType const& ThisNodes, ...
2. Initialize
3. Check
4. InitializeSolutionStep
5. InitializeNonLinearIteration
6. FinalizeNonLinearIteration
7. FinalizeSolutionStep
8. CalculateOnIntegrationPoints(const Variable& rVariable, ...
9. CalculateOnIntegrationPoints(const Variable<array_1d<double, 3>>& rVariable, ..
10. CalculateAll
11. InitializeElementVariables
12. CalculateAndAddLHS
13. CalculateAndAddCompressibilityMatrix
14. CalculateAndAddRHS
15. CalculateAndAddPermeabilityFlow
16. CalculateAndAddFluidBodyFlow
17. CalculateAndAddCompressibilityFlow
18. CalculateKinematics
19. GetNumberOfDOF
20. GetDofs

The other functions are not tested by now but they return zero values except CalculateOnIntegrationPoints in the case of PERMEABILITY_MATRIX

1. CalculateMassMatrix(MatrixType& rMassMatrix, const ProcessInfo&
   CurrentProcessInfo)
2. CalculateDampingMatrix(MatrixType& rDampingMatrix, const ProcessInfo& rCurrentProcessInfo)
3. GetValuesVector(Vector& rValues, int Step = 0)
4. GetFirstDerivativesVector(Vector& rValues, int Step = 0)
5. GetSecondDerivativesVector(Vector& rValues, int Step = 0)
6. CalculateOnIntegrationPoints(const Variable& rVariable, std::vector& rOutput, const ProcessInfo& rCurrentProcessInfo)

InitializeNonLinearIteration and FinalizeNonLinearIteration are empty, just override the base class functions.

Some of TransientPwElement functions use

1. UPwBaseElement::GetIntegrationMethod

2. UPwBaseElement::CalculateIntegrationCoefficients

3. UPwSmallStrainElement<TDim, TNumNodes>::ResetHydraulicDischarge

4. UPwSmallStrainElement<TDim, TNumNodes>::CalculateHydraulicDischarge

5. UPwSmallStrainElement<TDim, TNumNodes>::CalculateOnIntegrationPoints(const Variable& rVariable

6. UPwSmallStrainElement<TDim, TNumNodes>::CalculateDerivativesOfSaturation

7. UPwSmallStrainElement<TDim, TNumNodes>::CalculateDegreesOfSaturation

8. UPwSmallStrainElement<TDim, TNumNodes>::CalculateFluidFluxes

9. UPwSmallStrainElement<TDim, TNumNodes>::CalculateCompressibilityFlow

10. UPwSmallStrainElement<TDim, TNumNodes>::CalculatePermeabilityFlow

11. UPwSmallStrainElement<TDim, TNumNodes>::CalculateRelativePermeabilityValues

12. UPwSmallStrainElement<TDim, TNumNodes>::CalculateBishopCoefficients

13. UPwSmallStrainElement<TDim, TNumNodes>::CalculateFluidBodyFlow

14. UPwSmallStrainElement<TDim, TNumNodes>::InitializeNodalPorePressureVariables

15. UPwSmallStrainElement<TDim, TNumNodes>::InitializeNodalVolumeAccelerationVariables

16. UPwSmallStrainElement<TDim, TNumNodes>::InitializeProperties

In addition strategy and scheme classes call
17. UPwBaseElement::GetDofList
18. UPwBaseElement::CalculateLocalSystem
19. UPwBaseElement::CalculateRightHandSide
20. UPwBaseElement::EquationIdVector