Add merged Coriolis arrays in MOM_barotropic

[Hallberg-NOAA]

Replaced the 8 Coriolis parameter arrays ([abcd]zon and [abcd]mer) with merged 3-dimensional arrays (f_4_u and f_4_v), where the extra dimension is of size 4 and varies fastest. This reduces the number of arguments being passed around and it could improve performance by increasing the likelihood of cache hits. Also made the dgeo_de argument to set_up_BT_OBC() non-optional, which reduces the number of calls to this routine and should increase the chances it might be inlined. A few more spelling errors were corrected, and some notes added in comments highlighting potentially suspect reassignments of effective total gravities at open boundary condition points. All answers are bitwise identical and no external interfaces are changed.

[theresa-cordero]

I would like the to confirm that the dimensions 1 to 4 positions (southwest, southeast, etc.) are correctly labeled in the comments. It would be good to clarify in the comments that f_4_u is not located at a u, v, q, or tracer point but instead at a quarter grid point and the positions are relative to the u point.

Otherwise, I am happy with these changes. I think they add clarity to[abcd]mer and [abcd]zon while adding clarity to the code and simplifying the interfaces.

[Hallberg-NOAA]

Yes, @theresa-cordero, your interpretation here is correct about the actual staggering of these 4 variables. The previous variable names (a, b, c, d) date back to some classic papers by Akio Arakawa and collaborators, but is otherwise not very informative. The biggest change here is that these new arrays are now using the indexing of the points where they are used, whereas before the [abcd]zon variables used the indexing of the points where they are used for accelerations but the [abcd]mer variables used the indexing of the velocities whose contributions to the Coriolis accelerations they scaled. The new f_4_u and f_4_v variables are now always using the indexing of the accelerations they contribute to, which should make the code clearer.

[Hallberg-NOAA]

This PR has passed pipeline testing at https://gitlab.gfdl.noaa.gov/ogrp/mom6ci/MOM6/-/pipelines/27053.