Make `e3sm_to_cmip` its own task

[forsyth2]

Make e3sm_to_cmip its own task rather than being an optional part of the ts task.

[chengzhuzhang]

Some notes for using e3sm_to_cmip:

• land and atmosphere variables needs remapped nc files as input.
• MPAS variables depends on native outputs and need auxiliary files ( same as what MPAS analysis does)
• For v3 output, we will likely to add more variables in cmorized list
• cmorized data has a specific directory structure
• Consider try out the e3sm_to_cmip end-to-end script first.