remove redundant mesh files in cam - point to mesh files in ccs_config

### What is the feature/what would you like to discuss?

Currently, the ionosphere model and HEMCO (#560) use esmf mesh files set in the ```cam_physics_mesh``` nl in namelist_defaults.xml. Now that nuopc is the default coupler, we should just point to the mesh files in the grid definitions ccs_config/component_grids_nuopc.xml. Also the mesh files currently pointed to by cam_physics_mesh are duplicates contained in cesmdata/inputdata/atm/cam/coords/. We should try to only point to the CSEG mesh files maintained in cesmdata/inputdata/share/meshes/ since mesh files can be of dubious origin (b/c we have no centralized way of generating mesh and scrip files), and so we want a single repo where trusted mesh files are maintained.

### Is there anyone in particular you want to be part of this conversation?

_No response_

### Will this change (regression test) answers?

Yes

### Will you be implementing this enhancement yourself?

No