added linear dz in vertical grid

[alicebarthel]

Added option for linearly increasing dz in the ocean vertical grid (needed for the baroclinic gyre case)

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
• The E3SM-Project submodule has been updated with relevant E3SM changes
• The MALI-Dev submodule has been updated with relevant MALI changes
• Document (in a comment titled Testing in this PR) any testing that was used to verify the changes
• New tests have been added to a test suite

[cbegeman]

@alicebarthel The changes visually look good to me but I haven't tested them. Do you mind if I review and test this and the baroclinic gyre PR together, or do you have another idea in mind?

[alicebarthel]

@cbegeman whatever works better for you. Xylar and I had talked about making a separate branch and PR for the vertical grid changes, but since most of the changes were already updated by Xylar, this PR may be overkill.

[xylar]

@alicebarthel, yes, exactly. I thought the renaming still needed to happen but that's already on main so maybe this PR isn't needed after all. Sorry about that!

[alicebarthel]

No worries. I started the dev on a separate branch based on this (and rebased on yesterday's master). So maybe I'll switch this to a draft PR and make a bigger PR with the test case when I am ready.

[xylar]

You don't need to make a new PR for the test case, you just need to force-push to the branch you used for #547. I would prefer that to a new PR.