Some biomass outputs only updated for non-new cohorts

[samsrabin]

As part of cleaning up PR #1252, I found myself confused about something I did. This prompted me to do a deep dive on the VEGC biomass outputs to understand which are saved for all cohorts vs. only for non-new cohorts.

Variable	Search	sci.1.77.0_api.36.0.0
FATES_VEGC	ih_totvegc_si	All
FATES_VEGC_ABOVEGROUND	hio_agb_si	All
FATES_VEGC_PF	hio_biomass_si_pft	All
FATES_VEGC_SE_PF	hio_biomass_sec_si_pft	All
FATES_VEGC_AP	hio_biomass_si_age	All
FATES_VEGC_APPF	hio_biomass_si_agepft	Non-new
FATES_VEGC_ABOVEGROUND_SZPF	hio_agb_si_scpf	Non-new
FATES_VEGC_ABOVEGROUND_SZ	hio_agb_si_scls	Non-new
FATES_VEGC_SZ	hio_biomass_si_scls	Non-new
FATES_VEGC_SZPF	ih_totvegc_scpf	All

Specifically, during development of #1252 I discovered that summing FATES_VEGC_APPF across the age-class axis didn't result in the FATES_VEGC_PF values. I solved that by updating the former for every cohort, not just non-new ones.

This implies that non-new cohorts can have positive biomass, so they should never be skipped when processing biomass history outputs.

[samsrabin]

The NPLANT outputs have the same issue—at least the ones with per-ageclass axis are only calculated for non-new cohorts, but there are nonzero values in the new cohorts.

[samsrabin]

Here is a list of all variables that exclude new cohorts as of sci.1.78.3_api.36.1.0.

Only one variable is saved for new cohorts only: FATES_RECRUITMENT_CFLUX_PF.