Get global ocean resources and time steps based on mesh size

[xylar]

This merge switches many global ocean steps to getting the core count from either an estimate or exact number of cells in the mesh. Similarly, it switches to computing the time steps (both barotropic and baroclinic) from the minimum resolution of the mesh.

This work paves the way for generalized QU and icosahedral global ocean meshes.

Checklist

• User's Guide has been updated
• Developer's Guide has been updated
• API documentation in the Developer's Guide (api.rst) has any new or modified class, method and/or functions listed
• Documentation has been built locally and changes look as expected
• Document (in a comment titled Testing in this PR) any testing that was used to verify the changes

[xylar]

I'm still seeing hanging in my tests of this branch, similar to #629. In this case, it's for ocean/global_ocean/QU240/WOA23/performance_test/forward.

[xylar]

Testing

I ran the pr suite on Perlmutter, using the current main as a baseline. Many RK4 tests (perf, decomp, threads) fail the BFB comparison, as expected because the time step has changed (from 5 to 6 minutes). Similarly, EC(wISC)30to60 perf. tests are non-BFB because the time step changed from 5 to 15 minutes and btr_dt changed from 10 to 45 seconds.

All other tests are passing.

[xylar]

Retested on Chrysalis after merging #630 and rebasing. I'm seeing non-BFB results for the cosine bell on Chrysalis in addition to the 5 tests mentioned above. Differences are only for the QU60 test and are at roundoff.