Should add variables needed to calculate NBP into bc_out data structure

[ckoven]

In order for the host models to be able to calculate NBP, we need to pass to the host models all of the carbon fluxes leaving the FATES system. Currently we aren't passing fire emissions, instantaneous carbon losses to the atmosphere during land use change (conceptually overlapping with fire), grazing losses, and possibly others to come in the future.

@rosiealice has added some of the speciated fire emissions in NorESMhub#7. This is also related: ESCOMP/CTSM#1045.

We have an old issue on this point in #163. Since that is so old, I'll bring it up here again via this new issue so that it is closer to the top of the queue, as it is becoming more salient now.

[ckoven]

Update: I've done some work to include these and I believe I now have NBP and related variables working. Will issue PRs once I confirm correct behavior under a new spinup case.

FATES branch: ckoven/fates@twostream-restart-bugfixes-shijiefix...ckoven:fates:nbp_diagnostics
ELM commit: ckoven/E3SM@012f9c0