Perturbation/Increments for cold starts

[pjpegion]

Description

Currently the model can only read in an increment file if initializing with a restart file. This functionality is also used to read in ensemble perturbations, and should also work for a external initial condition. The solution is to move the call to read_da_inc outside the if external_ic/restart logic.

Fixes # (issue)

FV3 is not able to apply DA increment when cold staring #339

How Has This Been Tested?

So far, I have run limited regression tests on gaea, and tested that the perturbations are being read in during a cold start. The regression tests pass.

Checklist:

Please check all whether they apply or not

• My code follows the style guidelines of this project
• [ X I have performed a self-review of my own code
• [ X I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

[laurenchilutti]

Do you have a suggestion on from EMC or the UFS community can review this?

[lharris4]

@pjpegion @laurenchilutti This looks OK to me. There is no reason we can't use this method to apply to arbitrary initialization methods (restart, external_ic, or ideal).

[jkbk2004]

All tests are done ok at ufs-community/ufs-weather-model#2269. @bensonr @laurenchilutti can you merge this pr?