[SMApp] Element file sorting and foldering

[AlejandroCornejo]

📝 Description
Just creating folders to tidy the element list. Now is clearer and faster to find elements.

Since this change affects the directories of the StructuralMechanics elements, please ensure that your related Apps compile in this PR (commit changes if necessary).

CLApp and ContactSMApp have been updated.

@KratosMultiphysics/geomechanics I did minor updates but in my pc I could not compile your App due to unrelated (IMO) reasons:

/home/alejandro/Kratos/applications/GeoMechanicsApplication/custom_constitutive/linear_elastic_plane_strain_2D_law.cpp:58:1: error: function ‘Kratos::GeoLinearElasticPlaneStrain2DLaw::GeoLinearElasticPlaneStrain2DLaw(Kratos::GeoLinearElasticPlaneStrain2DLaw&&)’ defaulted on its redeclaration with an exception-specification that differs from the implicit exception-specification ‘’
   58 | GeoLinearElasticPlaneStrain2DLaw::GeoLinearElasticPlaneStrain2DLaw(GeoLinearElasticPlaneStrain2DLaw&& rOther) noexcept = default;
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/alejandro/Kratos/applications/GeoMechanicsApplication/custom_constitutive/linear_elastic_plane_strain_2D_law.cpp:59:35: error: function ‘Kratos::GeoLinearElasticPlaneStrain2DLaw& Kratos::GeoLinearElasticPlaneStrain2DLaw::operator=(Kratos::GeoLinearElasticPlaneStrain2DLaw&&)’ defaulted on its redeclaration with an exception-specification that differs from the implicit exception-specification ‘’
   59 | GeoLinearElasticPlaneStrain2DLaw& GeoLinearElasticPlaneStrain2DLaw::operator=(

@loumalouomega @philbucher @sunethwarna @rubenzorrilla @SergioJimenezReyes @ChengshunShang1996

[AlejandroCornejo]

Updated dir:

[matekelemen]

just wondering: why are the move constructor and move assignment operator defined out of line if they're defaulted? Especially since they're also noexcept, I would have imagined that inlining them is the way to go.