Add restart_coszen namelist option

[dabail10]

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• Short (1 sentence) summary of your PR:
  This adds a namelist option for adding coszen to the restart. This removes the need for CESMCOUPLED here.
• Developer(s):
  dabail10 (D. Bailey)
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• Please copy the PR test results link or provide a summary of testing completed below.
  https://github.com/CICE-Consortium/Test-Results/wiki/cice_by_mach_forks#cheyenne
• How much do the PR code changes differ from the unmodified code?
  • bit for bit
  • different at roundoff level
  • more substantial
• Does this PR create or have dependencies on Icepack or any other models?
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• Does this PR add any new test cases?
  • Yes
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• Is the documentation being updated? ("Documentation" includes information on the wiki or in the .rst files from doc/source/, which are used to create the online technical docs at https://readthedocs.org/projects/cice-consortium-cice/. A test build of the technical docs will be performed as part of the PR testing.)
  • Yes
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• Please provide any additional information or relevant details below:
  Several coupled models will need coszen on the restart file. This makes it a namelist option instead of an ifdef.

[dabail10]

See issue #486

[apcraig]

Great to see a cpp moved to namelist.

[apcraig]

@eclare108213, do you want to have a review before we merge?

[eclare108213]

Do changes also need to be made in io_binary/ice_restart.F90?

I would probably have put this new namelist flag in forcing_nml, since it's for a specific variable. We also have specific restart_[] flags in tracer_nml and zbgc_nml, for example. Maybe we should collect these into a new 'restart_nml' namelist, but not in this PR.

I just noticed an error in the documentation: in doc/source/user_guide_ug_case_settings.rst, please change 'restart' to 'history' in the comments for history_format. Thanks!

[dabail10]

Not sure that any coupled models use the binary restarts any longer, but I suppose this is a good plan.

[dabail10]

Maybe this is more appropriate in shortwave_nml?

[dabail10]

Actually, this is already handled for binary, because it is called from the generic write_restart_field/read_restart_field subroutines that are agnostic to the format. It's almost like someone designed them this way ... :)

[eclare108213]

Maybe this is more appropriate in shortwave_nml?

You could do that. My preference would still be forcing_nml, since coszen really is about the forcing, and the parameters in shortwave_nml are specific to the shortwave parameterizations.

[dabail10]

I've moved restart_coszen to the shortwave_nml namelist. I also made the updates to the documentation.