Add surface coupling layer for water tracers

### What is the feature/what would you like to discuss?

Add code to properly pass water tracer/isotope fields to their respective CMEPS coupling counterparts.

### Is there anyone in particular you want to be part of this conversation?

_No response_

### Will this change (regression test) answers?

Yes

### Will you be implementing this enhancement yourself?

Yes

Start by locating the existing surface coupling paths and the CMEPS counterparts for water tracer and isotope fields. Compare how related fields are passed and identify the regression test or answer set affected. Done means the tracer fields are correctly transferred and the regression answers are updated.

Written by the indexing model from the issue text.