Refactor geos-mesh tests to use meshes from a GEOS simulation

The idear is to have either small meshes built directly in the test file or meshes from a GEOS simulation to test all the function of geos-mesh.

Moreover, as geos-processing tests also use meshes from a GEOS simulation, and geos-proccessing is depending of geos-mesh, all the tests meshes are located in geos-mesh to reduce code duplication