diffusivities from internal tides ray tracing algo

[raphaeldussin]

For better readibility, the PR is split into 3 commits: the first deals with bugfixes and improvements relative to the internal tides energy (changes answers) while the second deals with refactoring of debugging infra. The third commit introduces the TKE loss to diffusivity part.

1st part:

(*)bugfixes for internal tides

- TKE_itidal_input values are set to zero where it is not applied to
  the model so that diagnostics are consistent

- removed useless halo updates

- diagnose energy loss terms as dE/dt instead of equivalent loss rate
  to properly close energy budget

- tot_vel_btTide2 was already a velocity squared, no need to square again

- Froude loss term was not properly initialized

- add missing halo updates for internal tide speed

- compute residual/critical slopes loss only where it has a meaning,
  allows to clean up noise in field

- uh/vh in energy flux routines do not need to be inout

- missing unit scaling for frequency

2nd part:

Refactor debugging internal tides

- put test for negative energy behind debug flag

- do energy budget in debug mode

- add flags to skip refraction, propagation for debugging

- add option to input TKE only at first step for debugging

- add checksums for unit scaling testing

- rewrite terms in refraction to avoid substractions of velocities

- rewrite gradient of coriolis in rotationally invariant form

last part:

Add internal tides diffusivities

- MOM_internal_tides gets new routine that converts
  TKE losses into diffusivities using the TKE_to_Kd array

- MOM_set_diffusivities handles the diagnostics

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 40.90%. Comparing base (9351353) to head (f6c9ef7).

Additional details and impacted files

@@             Coverage Diff              @@
##           dev/gfdl     #677      +/-   ##
============================================
+ Coverage     36.88%   40.90%   +4.01%     
============================================
  Files           271       42     -229     
  Lines         81692     5286   -76406     
  Branches      15269     1013   -14256     
============================================
- Hits          30132     2162   -27970     
+ Misses        45907     2939   -42968     
+ Partials       5653      185    -5468     

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[raphaeldussin]

Energy budget is closing:

[raphaeldussin]

also reproduces over processor counts with N = 480 and N = 441

[raphaeldussin]

@Hallberg-NOAA PR passes unit scaling tests in Boussinesq .and. Non-Boussinesq

[Hallberg-NOAA]

I have added a number of minor changes, mostly in the units of comments and in the dimensional rescaling factors, that I think need to be fixed with this latest revision to the code. None of these should be very complicated to address.

[Hallberg-NOAA]

I have inspected the updated code, and I believe that all issues that were identified previously have been resolved with this code contribution. Well done, @raphaeldussin.