Migrate a_min and m_min dynamics thresholds to namelist, rename to dyn_area_min and dyn_mass_min

[apcraig]

PR checklist

• Short (1 sentence) summary of your PR:
  Migrate a_min and m_min dynamics thresholds to namelist
• Developer(s):
  apcraig
• Suggest PR reviewers from list in the column to the right.
• Please copy the PR test results link or provide a summary of testing completed below.
  all results are bit-for-bit, full test suites run on derecho with CICE
• 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?
  • Yes
  • No
• Does this PR update the Icepack submodule? If so, the Icepack submodule must point to a hash on Icepack's main branch.
  • Yes
  • No
• Does this PR add any new test cases?
  • Yes
  • No
• 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
  • No, does the documentation need to be updated at a later time?
    • Yes
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• Please document the changes in detail, including why the changes are made. This will become part of the PR commit log.

Migrate a_min and m_min to namelist. These are the threshold values used to active dynamics calculations on a particular gridcell. a_min is the minimum area concentration (non-dimensional) and m_min is the minimum mass (kg/m2). Defaults are 0.001 (1/10th of 1%) and 0.01 (kg/m2) respectively.

Rename a_min and m_min to dyn_area_min and dyn_mass_min respectively.

Update documentation to add new namelist and update naming convention.

Closes #963

[apcraig]

I need some input for this PR. See also #963.

• Are we happy with the names a_min and m_min? Those variables become much more exposed moving them to namelist. Should we change them to something like dyn_amin and dyn_mmin or something? Please suggest something.

• Do we want a_min and m_min to be set independently? Or should we change the implementation so a_min is set and m_min is computed as a_min*10?

Once we finalize, I will complete testing. I have run quick_suites on derecho for 6 compilers so far and it's bit-for-bit.

[eclare108213]

I suggest dyn_area_min and dyn_mass_min.

[apcraig]

I updated the names to dyn_area_min and dyn_mass_min. I have run full test suites on derecho with Icepack and CICE and all testing looks good. Results are bit-for-bit. Will merge tomorrow unless there are other concerns.