Correct bug in kappa shear viscosity with vertex shear option.

[breichl]

• Viscosities at vertices along the coast were incorrectly zero'd out. This commit removes that mask so the non-zero shear driven viscosities can be interpolated from in the model. This bug caused diffusivities to be very large in channels and potentially near coastlines.
• A bugfix flag is added with an option to use the current behavior for legacy purposes.

Here is a sample shear driven diffusivity and viscosity at 50m depth in the Gibraltar region from a case with the bug flag as True:

Compared to with the fix:

[Hallberg-NOAA]

I agree with these changes. I have also examined the code that was not changed, and I have convinced myself that this will not be setting non-zero values for non-coastal land points.

[Hallberg-NOAA]

Please change the logging of the new runtime parameter VERTEX_SHEAR_VISCOSITY_BUG so that is only logged when it is relevant, as described in the comment following the relevant line of code.

[breichl]

Please change the logging of the new runtime parameter VERTEX_SHEAR_VISCOSITY_BUG so that is only logged when it is relevant, as described in the comment following the relevant line of code.

Done, thanks for this suggestion.

[Hallberg-NOAA]

Thank you for catching this bug and offering a correction.

[Hallberg-NOAA]

This has passed pipeline testing at https://gitlab.gfdl.noaa.gov/ogrp/mom6ci/MOM6/-/pipelines/26303 with the expected changes in some MOM_parameter_doc files due to a new runtime parameter.