Sparse interface update broke meshblockpacks

[Yurlungur]

The following code snippet now fails

/ /MeshBlockData *rc provided above somewhere
PackIndexMap imap;
rc->PackVariables(names, imap);

with errors that look like

/parthenon/src/interface/mesh_data.hpp:296:5: error: no matching function for call to ‘parthenon::MeshBlockData<double>::PackVariables(const std::vector<std::__cxx11::basic_string<char> >&, parthenon::PackIndexMap&, parthenon::PackIndexMap&, std::vector<std::__cxx11::basic_string<char> >&)’

This function signature is obviously wrong. Somehow the PackIndexMap is getting passed in twice. I believe this is because the API

We didn't catch this because for MeshBlockPack we apparently don't test this particular call signature anywhere. This needs to change, as it is used everywhere in the downstream codes.

[Yurlungur]

I notice also that it's now no longer possible to pass the coarse boolean through the mesh_data PackVariables machinery.