Fix to finish the reduction methods at the right time

Description

Adds next_output to the output buffer object and subroutines to determine when to finish the reduction and to set it (this is used with the time)
Adds logic to diag_manager_end so that it can do one last write if it is time to to
Refactors write_field_data to take in one field/buffer instead of an array
Adds getters for next_output and next_next_output

Fixes # (issue)

How Has This Been Tested? Before this update, there were answers changes such as

19790101.aerosol_daily_cmip.tile1.nc
DIFFER : VARIABLE : loadoa : POSITION : [0,0,0] : VALUES : 8.4246e-07 <> 8.24577e-07
DIFFER : VARIABLE : loadsoa : POSITION : [0,0,0] : VALUES : 2.4235e-07 <> 2.21925e-07
DIFFER : VARIABLE : loadso4 : POSITION : [0,0,0] : VALUES : 1.51636e-06 <> 1.54552e-06
DIFFER : VARIABLE : loadpoa : POSITION : [0,0,0] : VALUES : 6.0011e-07 <> 6.02652e-07

With this update they know reproduce. This was tested with one year long AM4 experiments.

Checklist:

[x] My code follows the style guidelines of this project
[x] I have performed a self-review of my own code
[x] I have commented my code, particularly in hard-to-understand areas
[x] I have made corresponding changes to the documentation
[x] My changes generate no new warnings
[x] Any dependent changes have been merged and published in downstream modules
[x] New check tests, if applicable, are included
[x] make distcheck passes

NOAA-GFDL / FMS

Fix to finish the reduction methods at the right time #1459