convert physconst thermodynamic routines into CCPP schemes

In CAM there are multiple thermodynamic calculation routines present in `physconst.F90` that are used by various dycores, including Spectral Element. However, given that these are "physics" calculations, and that in the future the physics itself might need access to these calculations, it might make sense to pull them out of `physconst.F90` and instead make them their own CCPP schemes, which would likely be stored in the NCAR `atmospheric_physics` repo under either `utilities` or another new directory, like "thermodynamics".

That being said, these thermodynamic routines are dependent on the chemical make-up of the atmosphere, and thus there will likely need to be a connection to chemistry, or at least any processes that sets or modifies the atmospheric composition being used in the simulation. Thus additional work might be needed to do this in a flexible and extensible way.