Add columns for relative test and time step to CSV file containing WE2E test info

[gsketefian]

DESCRIPTION OF CHANGES:

This PR modifies the script get_WE2Etest_names_subdirs_descs.sh that creates the CSV file containing test information the columns for relative cost and time step (DT_ATMOS). This allows users to have a better idea of what the cost of each test is (the relative cost is defined such that 1 unit represents the cost of running a single 6-hour forecast on the RRFS_CONUS_25km grid).

Other related changes:

• Add the flag generate_csv_file to the run_WE2E_tests.sh script to allow users to skip the CSV file generation step (since it can take a while).
• Use arguments for the function set_predef_grid_params() so that it can be called not just from the experiment generation scripts but also others (in this case from get_WE2Etest_names_subdirs_descs.sh). Necessary for this PR.
• Move some constants (NH0, NH3, NH4) from config_defaults.sh to constants.sh to make it easier to access them.
• Place the contents of constants.sh at the start of each experiment's var_defns.sh so that these constants are available to the j-jobs and ex-scripts when var_defns.sh is sourced.
• Use variable valid_vals_BOOLEAN in many more places (which allows many other valid_vals_... variables in valid_param_vals.sh and setup.sh to be removed).
• Several other bug fixes.

TESTS CONDUCTED:

The following tests (with results) were conducted on Hera. There were only three (previously existing) failures.

* grid_CONUS_25km_GFDLgrid_ics_FV3GFS_lbcs_FV3GFS_suite_GFS_v16:               SUCCESS
* grid_RRFS_CONUS_25km_ics_FV3GFS_lbcs_FV3GFS_suite_GFS_2017_gfdlmp:           SUCCESS
* grid_RRFS_CONUS_25km_ics_FV3GFS_lbcs_FV3GFS_suite_GFS_2017_gfdlmp_regional:  SUCCESS
* grid_RRFS_CONUS_25km_ics_FV3GFS_lbcs_FV3GFS_suite_GFS_v15p2:                 SUCCESS
* grid_RRFS_CONUS_25km_ics_FV3GFS_lbcs_FV3GFS_suite_GFS_v16:                   SUCCESS
* grid_RRFS_CONUS_25km_ics_FV3GFS_lbcs_RAP_suite_HRRR:                         SUCCESS
* grid_RRFS_CONUS_25km_ics_GSMGFS_lbcs_GSMGFS_suite_GFS_2017_gfdlmp:           SUCCESS
* grid_RRFS_CONUS_25km_ics_GSMGFS_lbcs_GSMGFS_suite_GFS_v15p2:                 SUCCESS
* grid_RRFS_CONUS_25km_ics_GSMGFS_lbcs_GSMGFS_suite_GFS_v16:                   FAILURE
* grid_RRFS_CONUS_25km_ics_NAM_lbcs_NAM_suite_HRRR:                            SUCCESS
* grid_RRFS_CONUS_25km_ics_NAM_lbcs_NAM_suite_RRFS_v1beta:                     SUCCESS
* grid_RRFS_CONUScompact_25km_ics_FV3GFS_lbcs_FV3GFS_suite_GFS_v16:            SUCCESS
* grid_RRFS_CONUScompact_25km_ics_HRRR_lbcs_HRRR_suite_HRRR:                   SUCCESS
* grid_RRFS_CONUScompact_25km_ics_HRRR_lbcs_HRRR_suite_RRFS_v1beta:            SUCCESS
* grid_RRFS_CONUScompact_25km_ics_HRRR_lbcs_RAP_suite_HRRR:                    SUCCESS
* grid_RRFS_CONUScompact_25km_ics_HRRR_lbcs_RAP_suite_RRFS_v1alpha:            SUCCESS
* grid_RRFS_CONUScompact_25km_ics_HRRR_lbcs_RAP_suite_RRFS_v1beta:             SUCCESS
* grid_SUBCONUS_Ind_3km_ics_FV3GFS_lbcs_FV3GFS_suite_GFS_v16:                  SUCCESS
* grid_SUBCONUS_Ind_3km_ics_HRRR_lbcs_RAP_suite_HRRR:                          SUCCESS
* grid_SUBCONUS_Ind_3km_ics_HRRR_lbcs_RAP_suite_RRFS_v1beta:                   SUCCESS
* GST_release_public_v1:                                                       SUCCESS
* MET_ensemble_verification:                                                   SUCCESS
* MET_verification:                                                            SUCCESS
* community_ensemble_008mems:                                                  SUCCESS
* community_ensemble_2mems:                                                    SUCCESS
* custom_ESGgrid:                                                              SUCCESS
* custom_GFDLgrid:                                                             SUCCESS
* custom_GFDLgrid__GFDLgrid_USE_GFDLgrid_RES_IN_FILENAMES_eq_FALSE:            SUCCESS
* custom_GFDLgrid__GFDLgrid_USE_GFDLgrid_RES_IN_FILENAMES_eq_TRUE:             SUCCESS
* deactivate_tasks:                                                            SUCCESS
* get_from_HPSS_ics_FV3GFS_lbcs_FV3GFS_fmt_grib2_2019061200:                   SUCCESS
* get_from_HPSS_ics_FV3GFS_lbcs_FV3GFS_fmt_grib2_2019101818:                   SUCCESS
* get_from_HPSS_ics_FV3GFS_lbcs_FV3GFS_fmt_grib2_2020022518:                   SUCCESS
* get_from_HPSS_ics_FV3GFS_lbcs_FV3GFS_fmt_grib2_2020022600:                   SUCCESS
* get_from_HPSS_ics_FV3GFS_lbcs_FV3GFS_fmt_grib2_2021010100:                   SUCCESS
* get_from_HPSS_ics_FV3GFS_lbcs_FV3GFS_fmt_nemsio:                             SUCCESS
* get_from_HPSS_ics_FV3GFS_lbcs_FV3GFS_fmt_nemsio_2019061200:                  SUCCESS
* get_from_HPSS_ics_FV3GFS_lbcs_FV3GFS_fmt_nemsio_2019101818:                  SUCCESS
* get_from_HPSS_ics_FV3GFS_lbcs_FV3GFS_fmt_nemsio_2020022518:                  SUCCESS
* get_from_HPSS_ics_FV3GFS_lbcs_FV3GFS_fmt_nemsio_2020022600:                  SUCCESS
* get_from_HPSS_ics_FV3GFS_lbcs_FV3GFS_fmt_nemsio_2021010100:                  SUCCESS
* get_from_HPSS_ics_FV3GFS_lbcs_FV3GFS_fmt_netcdf_2021062000:                  SUCCESS
* get_from_HPSS_ics_GSMGFS_lbcs_GSMGFS:                                        SUCCESS
* get_from_HPSS_ics_HRRR_lbcs_RAP:                                             SUCCESS
* get_from_HPSS_ics_RAP_lbcs_RAP:                                              SUCCESS
* get_from_NOMADS_ics_FV3GFS_lbcs_FV3GFS_fmt_nemsio:                           SUCCESS
* inline_post:                                                                 SUCCESS
* nco_ensemble:                                                                SUCCESS
* nco_inline_post:                                                             SUCCESS
* pregen_grid_orog_sfc_climo:                                                  SUCCESS
* specify_DOT_OR_USCORE:                                                       SUCCESS
* specify_DT_ATMOS_LAYOUT_XY_BLOCKSIZE:                                        SUCCESS
* specify_EXTRN_MDL_SYSBASEDIR_ICS_LBCS:                                       SUCCESS
* specify_RESTART_INTERVAL:                                                    SUCCESS
* specify_template_filenames:                                                  SUCCESS
* subhourly_post:                                                              FAILURE
* subhourly_post_ensemble_2mems:                                               FAILURE

DOCUMENTATION:

Documentation is updated via PR #278 in the ufs-srweather-app repo.

[danielabdi-noaa]

I tested this on Hera -- looks good to me.