Scalar diag conversion; Q and R dimension scaling

[marshallward]

This patch adds support for enthalpy (Q) and density (R) dimensional
scaling into the test suite.

It also resolves an issue with conversion scaling in scalars
(post_data_0d) which were not being applied, and make it impossible to
verify the dimensions of scalar diagnostics.

[codecov-io]

Codecov Report

Merging #1103 into dev/gfdl will decrease coverage by 2.24%.
The diff coverage is 49.92%.

@@             Coverage Diff              @@
##           dev/gfdl    #1103      +/-   ##
============================================
- Coverage     45.76%   43.52%   -2.25%     
============================================
  Files           215      214       -1     
  Lines         69638    69361     -277     
============================================
- Hits          31872    30186    -1686     
- Misses        37766    39175    +1409     

Impacted Files	Coverage Δ
config_src/solo_driver/MESO_surface_forcing.F90	0.00% <0.00%> (ø)
config_src/solo_driver/MOM_surface_forcing.F90	27.90% <0.00%> (ø)
...nfig_src/solo_driver/Neverland_surface_forcing.F90	0.00% <0.00%> (ø)
config_src/solo_driver/user_surface_forcing.F90	0.00% <0.00%> (ø)
src/core/MOM_PressureForce_analytic_FV.F90	44.18% <ø> (ø)
src/core/MOM_variables.F90	57.77% <ø> (ø)
src/diagnostics/MOM_debugging.F90	13.21% <0.00%> (-0.08%)	⬇️
src/ice_shelf/MOM_ice_shelf.F90	0.00% <0.00%> (ø)
src/ice_shelf/MOM_marine_ice.F90	0.00% <0.00%> (ø)
...ameterizations/lateral/MOM_mixed_layer_restrat.F90	87.26% <0.00%> (ø)
... and 68 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1c44924...3a04ca5. Read the comment docs.

[Hallberg-NOAA]

The pipeline tests on this commit are at https://gitlab.gfdl.noaa.gov/ogrp/MOM6/pipelines/10335.

[Hallberg-NOAA]

This contribution is useful and correct, bringing the treatment of the conversion factor in post_data_0d into consistency with the other versions of post_data, and expanding the range of units subject to automated testing.