[BugFix] shear wave test

The lattice Boltzmann step tries to figure out a stencil on its own, when no stencil is provided in the config class. This did not work in the shear wave test. The suggestion here is to just state the stencil in the config file

tests/full_scenarios/shear_wave/scenario_shear_wave.py

@@ -202,19 +202,19 @@ def create_full_parameter_study():
 
     config = CreateKernelConfig(target=Target.CPU)
 
-    methods = [LBMConfig(method=Method.TRT, relaxation_rates=[omega, 1]),
-               LBMConfig(method=Method.MRT, relaxation_rates=[omega], equilibrium_order=2),
-               LBMConfig(method=Method.MRT, relaxation_rates=[omega], equilibrium_order=3),
-               LBMConfig(method=Method.CUMULANT, relaxation_rates=[omega],  # cumulant
+    methods = [LBMConfig(stencil=LBStencil(Stencil.D3Q27), method=Method.TRT, relaxation_rates=[omega, 1]),
+               LBMConfig(stencil=LBStencil(Stencil.D3Q27), method=Method.MRT, relaxation_rates=[omega],
+                         equilibrium_order=2),
+               LBMConfig(stencil=LBStencil(Stencil.D3Q27), method=Method.MRT, relaxation_rates=[omega],
+                         equilibrium_order=3),
+               LBMConfig(stencil=LBStencil(Stencil.D3Q27), method=Method.CUMULANT, relaxation_rates=[omega],  # cumulant
                          compressible=True, continuous_equilibrium=True, equilibrium_order=3),
-               LBMConfig(method=Method.CUMULANT, relaxation_rates=[omega],  # cumulant with fourth-order correction
+               LBMConfig(stencil=LBStencil(Stencil.D3Q27), method=Method.CUMULANT, relaxation_rates=[omega],  # cumulant with fourth-order correction
                          compressible=True, continuous_equilibrium=True, fourth_order_correction=0.1),
-               LBMConfig(method=Method.TRT_KBC_N4, relaxation_rates=[omega, omega_f], entropic=True,
-                         zero_centered=False,  # entropic order 2
-                         continuous_equilibrium=True, equilibrium_order=2),
-               LBMConfig(method=Method.TRT_KBC_N4, relaxation_rates=[omega, omega_f], entropic=True,
-                         zero_centered=False,  # entropic order 3
-                         continuous_equilibrium=True, equilibrium_order=3),
+               LBMConfig(stencil=LBStencil(Stencil.D3Q27), method=Method.TRT_KBC_N4, relaxation_rates=[omega, omega_f],
+                         entropic=True, zero_centered=False, continuous_equilibrium=True, equilibrium_order=2),
+               LBMConfig(stencil=LBStencil(Stencil.D3Q27), method=Method.TRT_KBC_N4, relaxation_rates=[omega, omega_f],
+                         entropic=True, zero_centered=False, continuous_equilibrium=True, equilibrium_order=3),
 
                # entropic cumulant: not supported for the moment
                # LBMConfig(method=Method.CUMULANT, relaxation_rates=["omega", "omega_f"], entropic=True, zero_centered=False,