Add netCDF support to ghg_process

[jfahlen]

Adds support to ghg_process for reading both ENVI and netCDF files from the DAAC.

1. There are only 3 netCDF input files compared to 7 ENVI input files because several fields that are distant files in ENVI are combined into one netCDF file. As a result, there are redundant inputs. This could probably be streamlined, but anyway.
2. The glt file is not moved to netcdf. I wasn't sure if this should be done or not.
3. This is not as clean an implementation as I'd hoped because there are not equivalent files. For example, there is no loc netCDF file.

Example ENVI ghg_process calls:
python ghg_process.py /beegfs/store/emit/ops/data/acquisitions/20230810/emit20230810t051516/l1b/emit20230810t051516_o22204_s000_l1b_rdn_b0106_v01.img /beegfs/store/emit/ops/data/acquisitions/20230810/emit20230810t051516/l1b/emit20230810t051516_o22204_s000_l1b_obs_b0106_v01.img /beegfs/store/emit/ops/data/acquisitions/20230810/emit20230810t051516/l1b/emit20230810t051516_o22204_s000_l1b_loc_b0106_v01.img /beegfs/store/emit/ops/data/acquisitions/20230810/emit20230810t051516/l1b/emit20230810t051516_o22204_s000_l1b_glt_b0106_v01.img /beegfs/store/emit/ops/data/acquisitions/20230810/emit20230810t051516/l1b/emit20230810t051516_o22204_s000_l1b_bandmask_b0106_v01.img /beegfs/store/emit/ops/data/acquisitions/20230810/emit20230810t051516/l2a/emit20230810t051516_o22204_s000_l2a_mask_b0106_v01.img /beegfs/scratch/jfahlen/test_netcdf/emit20230810t051516_envi --state_subs /beegfs/store/emit/ops/data/acquisitions/20230810/emit20230810t051516/l2a/emit20230810t051516_o22204_s000_l2a_statesubs_b0106_v01.img --overwrite

Equivalent call using netCDF files downloaded from LP DAAC:
python ghg_process.py /beegfs/scratch/jfahlen/test_netcdf/EMIT_L1B_RAD_001_20230810T051516_2322204_013.nc /beegfs/scratch/jfahlen/test_netcdf/EMIT_L1B_OBS_001_20230810T051516_2322204_013.nc /beegfs/scratch/jfahlen/test_netcdf/EMIT_L1B_RAD_001_20230810T051516_2322204_013.nc /beegfs/store/emit/ops/data/acquisitions/20230810/emit20230810t051516/l1b/emit20230810t051516_o22204_s000_l1b_glt_b0106_v01.img /beegfs/scratch/jfahlen/test_netcdf/EMIT_L2A_MASK_001_20230810T051516_2322204_013.nc /beegfs/scratch/jfahlen/test_netcdf/EMIT_L2A_MASK_001_20230810T051516_2322204_013.nc /beegfs/scratch/jfahlen/test_netcdf/emit20230810t051516 --state_subs /beegfs/scratch/jfahlen/test_netcdf/EMIT_L2A_MASK_001_20230810T051516_2322204_013.nc --overwrite