Sync bathymetry face_z and node_z array sizes with meshkernel

[veenstrajelmer]

Is your feature request related to a problem? Please describe.
The bathymetry properties of Mesh2d and probably other classes are not synced with meskernel. In test_read_net_nc_2d_without_faces it happens that face_x.size=208 and face_z.size=0 (although node_z is not empty, so this is actually sort of correct). This is also the case with bathymetry clipping as was documented in Deltares/MeshKernel#326

Describe the solution you'd like
Some smartness in bathymetry setting/maintaining z-values. Preferably as part of meshkernel(py), but otherwise think of a way to handle it properly in hydrolib-core.

Maybe also for edge_z? This is currently no property of Mesh2d.