Cannot set different land default settings for different compsets/tri-grid resolutions

Many land default settings (e.g., finidat, fsurdat) are currently controlled by `namelist_defaults_clm4_5.xml`, which only uses the land resolutions to select different settings. This causes more problems when we move to the tri-grid. Many compsets share the same tri-grid land grid.

For instance, the v2 atmosphere RRM resolutions all use the r0125 land grid. This PR https://github.com/E3SM-Project/E3SM/pull/3449 adds the default finidat for antarcticax4v1_r0125_antarcticax4v1.F2010SC5-CMIP6. Similar changes are required for northamericax4v1_r0125_northamericax4v1.F2010SC5-CMIP6. However, we cannot do that without changing the default antarcticax4v1_r0125_antarcticax4v1.F2010SC5-CMIP6.

@rljacob , is there a way to fix this issue?

Read namelist_defaults_clm4_5.xml and compare the default finidat change described in PR 3449 with the northamericax4v1 case. Trace how compsets and tri-grid land resolutions select defaults, then verify that both v2 atmosphere RRM cases can receive distinct land defaults without changing the other case.

Written by the indexing model from the issue text.