CDAT migration: Fix African easterly wave density plots in TC analysis and convert H20LNZ units to ppm/volume

[tomvothecoder]

Description

• Related to #851 -- looks like I already addressed this on cdat-migration-fy24 but I refactored it a bit more
• Related to #874
• Relatedt to #871

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] My changes generate no new warnings
• [x] Any dependent changes have been merged and published in downstream modules

If applicable:

• [ ] New and existing unit tests pass with my changes (locally and CI/CD build)
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have noted that this is a breaking change for a major release (fix or feature that would cause existing functionality to not work as expected)

[tomvothecoder]

@tomvothecoder I think the changes in .cfg files for H2OLNZ units change are not brought in this PR: #874 (files)

For that specific PR, the changes are already here. Example: https://github.com/E3SM-Project/e3sm_diags/blob/3df16d2266c98f526fe03ebeecb68c6170d61618/e3sm_diags/driver/default_diags/zonal_mean_2d_stratosphere_model_vs_obs.cfg#L65-L75

I rebased the dev branch on the latest main, which pulls in changes to .cfg files. I don't need to update any .cfg files in this PR.

[chengzhuzhang]

@tomvothecoder Just a heads-up that this PR is also just merged: https://github.com/E3SM-Project/e3sm_diags/pull/879 and we need to bring to migration branch..

[tomvothecoder]

@tomvothecoder Just a heads-up that this PR is also just merged: #879 and we need to bring to migration branch..

Done