Change use of "potential veg" for FATES interface code to all_primary_land

Change use of "Potential veg" in FATES interface code to reference "primary land". This will also entail updating FATES to a version where this change comes in.

The FATES side issue for this is here:

https://github.com/NGEET/fates/issues/1374

The namelist variable: use_fates_potentialveg would change to use_fates_all_primary_land

And the PVT test should change as follows:

I'd like to have a longer more descriptive name for the PVT test. Maybe something like FATES_LUH2_FROM_SPINUP?

_Originally posted by @ekluzek in https://github.com/ESCOMP/CTSM/pull/2507#discussion_r1674791271_