ctsm5.4.039: add new fates namelist switch for dbh init when nocomp is on

[mvdebolskiy]

Description of changes

This change is coordinated with FATES PR NGEET/fates#1550.

Adds a switch for initializing patches with dbh instead of density for nocomp runs.

Specific notes

Contributors other than yourself, if any:

CTSM Issues Fixed (include github issue #):

Are answers expected to change (and if so in what way)?

No, switch is off by default

Any User Interface Changes (namelist or namelist defaults changes)?

use_fates_dbh_ini is added.

Does this create a need to change or add documentation? Did you do so?

Testing performed, if any:

ERS_D_Ld20.f45_f45_mg37.I2000Clm60FatesCrujraRs.derecho_intel.clm-FatesColdTwoStreamNoCompFixedBioGeo

Passed with diffs when use_fates_dbh_init=.true.
Without that namelist change bfb.

NOTE: Be sure to check your coding style against the standard
(https://github.com/ESCOMP/ctsm/wiki/CTSM-coding-guidelines) and review
the list of common problems to watch out for
(https://github.com/ESCOMP/CTSM/wiki/List-of-common-problems).

[glemieux]

Per the ctsm-fates standup this morning, @mvdebolskiy is going to add a test for the new namelist option that will update the fates_recruit_init_seed on the fly.

[mvdebolskiy]

@glemieux Should I also add an SP test?
I have ERS_D_Ld10.f45_f45_mg37.I2000Clm50FatesCruRsGs.derecho_intel.clm-FatesColdNoCompInitDbh in the queue right now. Will let you know if it goes through.
Test passed.

[glemieux]

@glemieux Should I also add an SP test?

Not at this point, I think. It currently wouldn't end up doing anything since during initialization fates sp mode calculates the initial dbh from a hard-coded height value:
https://github.com/NGEET/fates/blob/b17b0bdff243c6782414e191736fb0d15935a5c7/main/EDInitMod.F90#L1349-L1381

Maybe there is a case to allow the user to change this initial dbh directly instead of calculating it from using the satellite phenology data, but I don't think so (at least not at this point). It would also require a bit of refactor to the sp mode initialization calls. CC'ing @adrifoster for her thoughts.

[glemieux]

Starting fates regression testing.