New s2dv_cube testing

Hi @vagudets @erifarov

As we discussed yesterday, the new s2dv_cube is ready to be tested in verification tool. The development is under this branch https://earth.bsc.es/gitlab/external/cstools/-/tree/develop-new_s2dv_cube. The plan is (correct me if I'm wrong):

• I test the Loading module, checking if the output of as.s2dv_cube() after each loading is reasonable. I will also create unit tests (since more changes in s2dv_cube in the future is expected.)
• @vagudets and I test the rest of the modules. It is not urgent work, so let's say in February we can start doing this.

Cheers,
An-Chi