Fix plumber2_surf_wrapper

[samsrabin]

Description of changes

• Include --lon-type 180 in subset_data command to avoid ambiguity.
• If PLUMBER2 sites CSV file has -999 for a pft number, do not set that to zero—instead, just don't include a second PFT.
• Respect whether user requested a 16- or 78-PFT file.
• Add --overwrite option.
• Add --plumber2-sites-csv option to specify CSV file path.
• Add argument parser unit testing.
• Add system testing.
• Error on subset_data failure.

Specific notes

Contributors other than yourself, if any: None

CTSM Issues Fixed: Resolves #3262

Are answers expected to change (and if so in what way)? No

Any User Interface Changes (namelist or namelist defaults changes)? No

Does this create a need to change or add documentation? Did you do so? No

Testing performed, if any: As of c325805:

• Manual testing with commands given in plumber2_surf_wrapper: Some files not produced #3262
• The 62 files originally being produced (at 761bb47) aren't affected.
• Python unit tests
• Python system tests
• clm_pymods suite: /glade/derecho/scratch/samrabin/tests_0620-185305de/

[ekluzek]

@samsrabin and I went over this. And this is great work and I'm glad to see it come in. It fixes problems, but also makes the code more robust, with better error handling, AND it adds good testing for all this. So this will save the project time downstream.

I added a few comments/questions here that @samsrabin will decide on. I'm happy to approve it and have it come in shortly.