Extract core functionality from mesh module into a new module
This MR introduces a split of the mesh module into two separate modules, where "mesh_common" extracts some core functionality from "mesh". mesh_common contains the core functionality/coupling to OpenMesh (ie. general mesh computations, vtk). Its dependencies are strongly reduced to just core and vtk (+OpenMesh).
The mesh module is basically the old module minus the code extracted to mesh_common, depending on mesh_common. It has quite a set of dependencies and represents the addition of meshes to a multitude of modules in walberla.
This split allows us to introduce meshes to MESA-PD without dragging along all dependencies of the mesh module.