Axisymmetric geometry support in NLFormIntegrators

[CINTROINI]

Currently, the implementation assumes a Cartesian formulation only. This issue aims to extend all NLFormIntegrators so that they are fully compatible with axisymmetric geometries.

This modification should ensure consistency across all NLFormIntegrators, including the appropriate geometric weighting terms in Integrators.

Future work may extend this design to support additional geometries (e.g. cylindrical or spherical), following the same abstraction pattern.

[CINTROINI]

To enable simulations on axisymmetric geometries, the current definition of the Problem class needs to be enhanced. The proposed modification is as follows:

    PB Heat_pb("Heat", oper, heat_vars, {coef_pb}, pst);
    Heat_pb.setGeometry(Geometry::Axisymmetric);

By default, the geometry will be set to Geometry::Cartesian if no specific geometry is defined.

Additional Note on Source Terms:

When defining a source term on an Operator, ensure that it is multiplied by the radius. This multiplication is automatically handled by all integrators. However, source terms defined in the input datafile will not be automatically adjusted and must be manually multiplied by the radius.