Too long test cases
The long-run pipeline gives the following output:
13475.37s call lbmpy_tests/test_conserved_quantity_relaxation_invariance.py::test_srt
1078.84s call lbmpy_tests/test_diffusion.py::test_diffusion
505.76s call lbmpy_tests/centeredcumulant/test_flow_around_sphere.py::test_flow_around_sphere_long[True-Stencil.D3Q27]
460.70s call lbmpy_tests/centeredcumulant/test_flow_around_sphere.py::test_flow_around_sphere_long[False-Stencil.D3Q27]
243.29s call lbmpy_tests/centeredcumulant/test_flow_around_sphere.py::test_flow_around_sphere_long[False-Stencil.D3Q19]
218.93s call lbmpy_tests/centeredcumulant/test_flow_around_sphere.py::test_flow_around_sphere_short[False-Stencil.D3Q27]
214.62s call lbmpy_tests/centeredcumulant/test_flow_around_sphere.py::test_flow_around_sphere_short[True-Stencil.D3Q27]
178.90s call lbmpy_tests/phasefield/test_n_phase_boyer_analytical.ipynb::lbmpy_tests/phasefield/test_n_phase_boyer_analytical.ipynb
174.18s call lbmpy_tests/test_central_moment.py::test_central_moment_ldc
172.26s call lbmpy_tests/test_float_kernel.py::test_scenario[Method.CENTRAL_MOMENT-True]
167.89s call lbmpy_tests/test_float_kernel.py::test_scenario[Method.CENTRAL_MOMENT-False]
152.72s call lbmpy_tests/test_force.py::test_modes_central_moment_longrun[False-ForceModel.SIMPLE-Stencil.D3Q27]
148.64s call lbmpy_tests/test_force.py::test_modes_central_moment_longrun[False-ForceModel.KUPERSHTOKH-Stencil.D3Q27]
133.62s call lbmpy_tests/centeredcumulant/test_equilibrium.py::test_equilibrium_pdfs[PdfsToCentralMomentsByMatrix-Stencil.D3Q27]
133.46s call lbmpy_tests/test_float_kernel.py::test_scenario[Method.CUMULANT-False]
129.22s call lbmpy_tests/test_float_kernel.py::test_scenario[Method.CUMULANT-True]
122.35s call lbmpy_tests/test_central_moment_transform.py::test_backward_transform[Stencil.D3Q27-polynomial]
121.65s call lbmpy_tests/test_force.py::test_modes_central_moment_longrun[False-ForceModel.GUO-Stencil.D3Q27]
120.27s call lbmpy_tests/test_force.py::test_modes_central_moment_longrun[False-ForceModel.SHANCHEN-Stencil.D3Q27]
119.87s call lbmpy_tests/centeredcumulant/test_equilibrium.py::test_equilibrium_pdfs[FastCentralMomentTransform-Stencil.D3Q27]
Especially, the first two test cases should be shortened