32-bit physics with FV3_RAP

[SamuelTrahanNOAA]

This adds support for 32-bit physics to the FV3, based on prior work on the Neptune model. The 64-bit physics should not change results. The only change in this repository is to add a flag to enable single precision. The code for that was copied from the authoritative branch.

See the top-level PR here for details:

ufs-community/ufs-weather-model#1215

The issue for this is here:

ufs-community/ufs-weather-model#1288

[RobertPincus]

@SamuelTrahanNOAA The dtc/ccpp branch has been maintained by @dustinswales. We could incorporate this single change but it would sure be nicer to have the branch updated with all changes to main. I dunno if Dustin has time to manage this, or what the flow should be since this branch is specific to UFS (CCPP)/

[SamuelTrahanNOAA]

This PR is a major change in FV3 and CCPP, so I don't want to add any other changes. Also, it is absolutely critical that this PR not change the results of any tests on any platform. I do agree that we need to update dtc/ccpp from master, but that is outside the scope of this PR, and belongs in another.