Allow for variable renaming in coupled modeling

[Arcomano1234]

Currently, we are attempting to mix and match an atmospheric model trained on ERA5 and an ocean model trained on UFS replay dataset. The problem is in ERA5 wind stresses are called eastward_surface_stress while in CM4 and UFS replay they are called eastward_surface_wind_stress. Given that we will not be using the atmospheric variables to train a new ACE version for the foreseeable future we need a way to allow variable renaming. Similar to how it was done for HiRO-ACE in the downscaling model, this PR adds an optional stepper arg atmosphere_output_rename that will remap the user specified atmospheric variables to be renamed when the ocean model is grabbing forcing variables. Can also be used during inference and standalone eval.

Changes:

• add atmosphere_output_rename to coupled stepper that can rename atmospheric forcing variables for the ocean model

• Tests added

[oliverwm1]

I think this would be a reasonable feature to support. Although in my experience there are always a lot of tricky edge cases. Previously we had support for renaming variables within data loading, but we removed this due to the complexity of supported merged datasets: https://github.com/ai2cm/full-model/pull/1511. Keeping it confined to the coupled stepper for now at least limits surface area.