Eliminate unneeded variables in diabatic_driver

[Hallberg-NOAA]

Eliminated unnecessary variables and some repetitive calculations from
diabatic_driver.F90. Also replaced G%ke with GV%ke in this file and added
units to some defining comments. All answers and output are bitwise identical.

[codecov-io]

Codecov Report

Merging #1267 (b9ae6f9) into dev/gfdl (e7e6c4a) will decrease coverage by 0.02%.
The diff coverage is 79.54%.

@@             Coverage Diff              @@
##           dev/gfdl    #1267      +/-   ##
============================================
- Coverage     45.78%   45.76%   -0.03%     
============================================
  Files           225      225              
  Lines         71458    71435      -23     
============================================
- Hits          32714    32689      -25     
- Misses        38744    38746       +2     

Impacted Files	Coverage Δ
...parameterizations/vertical/MOM_diabatic_driver.F90	63.96% <79.54%> (-0.48%)	⬇️
...rameterizations/vertical/MOM_diapyc_energy_req.F90	0.00% <0.00%> (-0.45%)	⬇️

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[marshallward]

https://gitlab.gfdl.noaa.gov/ogrp/MOM6/-/pipelines/11658 ✔️