Add creation of src.cupid for CESM

For CESM cases we'd like to have a $CASEROOT/SourceMods/src.cupid source mods directory created so that user config YAML files could be used rather than the templates from CUPiD itself.

the issue on the CUPiD side is here:

https://github.com/NCAR/CUPiD/issues/378

Looking at the code on how to implement this.

CIME/case/case.py

creates the SourceMod directories in the _create_caseroot_sourcemods subroutine.

Probably the way to do this would be to have an if statement that extends the component array with cupid if the model is CESM.

``` python
if case.get_value("MODEL") == "cesm":
components.extend(["cupid"])
```

This is related to #4939