[T/LF] HydraulicFlow test. Verifiable on sfc.flux.

When compared to the surface flux the numbers for hydraulic flow
(aside from the boundary effects) are equal (scaled byth the
surface element area).

ProcessLib/LiquidFlow/Tests.cmake

@@ -378,6 +378,8 @@ AddTest(
     cube_1x1x1_hex_1e3_complete_surface_left_right_dirichlet_specific_flux_t_0.864000_expected.vtu cube_1x1x1_hex_1e3_complete_surface_left_right_dirichlet_specific_flux_t_0.864000.vtu specific_flux specific_flux 1e-7 1e-13
     LF_cube_1e3_calculatesurfaceflux_pcs_0_ts_1_t_0.432000_expected.vtu LF_cube_1e3_calculatesurfaceflux_pcs_0_ts_1_t_0.432000.vtu pressure pressure 1e-7 1e-13
     LF_cube_1e3_calculatesurfaceflux_pcs_0_ts_2_t_0.864000_expected.vtu LF_cube_1e3_calculatesurfaceflux_pcs_0_ts_2_t_0.864000.vtu pressure pressure 1e-7 1e-13
+    LF_cube_1e3_calculatesurfaceflux_pcs_0_ts_1_t_0.432000_expected.vtu LF_cube_1e3_calculatesurfaceflux_pcs_0_ts_1_t_0.432000.vtu HydraulicFlow HydraulicFlow 1e-13 0
+    LF_cube_1e3_calculatesurfaceflux_pcs_0_ts_2_t_0.864000_expected.vtu LF_cube_1e3_calculatesurfaceflux_pcs_0_ts_2_t_0.864000.vtu HydraulicFlow HydraulicFlow 1e-13 0
 )
 
 AddTest(