CESM test suite does not compare mom6.h.bgc.native history files

I added two new fields to the `mom6.h.bgc.native` stream in https://github.com/NCAR/MOM6/pull/419 and went looking for `cprnc` output confirming the change... instead I found that we are comparing `h.bgc.z` but not `h.bgc.native`:

```
$ ls *mom6.h.*.nc.cprnc.out
ERS.TL319_t232.G1850MARBL_JRA.derecho_intel.GC.20260411_092035_zdv47l.mom6.h.bgc.z.0001-01-11.nc.cprnc.out
ERS.TL319_t232.G1850MARBL_JRA.derecho_intel.GC.20260411_092035_zdv47l.mom6.h.native.0001-01-11.nc.cprnc.out
ERS.TL319_t232.G1850MARBL_JRA.derecho_intel.GC.20260411_092035_zdv47l.mom6.h.ocean_geometry.nc.cprnc.out
ERS.TL319_t232.G1850MARBL_JRA.derecho_intel.GC.20260411_092035_zdv47l.mom6.h.rho2.0001-01-11.nc.cprnc.out
ERS.TL319_t232.G1850MARBL_JRA.derecho_intel.GC.20260411_092035_zdv47l.mom6.h.sfc.0001-01-11.nc.cprnc.out
ERS.TL319_t232.G1850MARBL_JRA.derecho_intel.GC.20260411_092035_zdv47l.mom6.h.static.nc.cprnc.out
ERS.TL319_t232.G1850MARBL_JRA.derecho_intel.GC.20260411_092035_zdv47l.mom6.h.z.0001-01-11.nc.cprnc.out
```

For that specific PR I was able to compare files by hand:

```
$ my_ncdiff ../../ERS.TL319_t232.G1850MARBL_JRA.derecho_intel.G.20260410_135953_nhg5ae/run/ERS.TL319_t232.G1850MARBL_JRA.derecho_intel.G.20260410_135953_nhg5ae.mom6.h.bgc.native.0001-01-11.nc ERS.TL319_t232.G1850MARBL_JRA.derecho_intel.GC.20260411_092035_zdv47l.mom6.h.bgc.native.0001-01-11.nc
Modify: 2026-04-11 00:54:49.000000000 -0600
Modify: 2026-04-11 19:04:47.000000000 -0600
/glade/u/apps/opt/ncl/6.6.2/bin/ncl
Copyright (C) 1995-2019 - All Rights Reserved
University Corporation for Atmospheric Research
NCAR Command Language Version 6.6.2
The use of this software is governed by a License Agreement.
See http://www.ncl.ucar.edu/ for more details.
Comparing ../../ERS.TL319_t232.G1850MARBL_JRA.derecho_intel.G.20260410_135953_nhg5ae/run/ERS.TL319_t232.G1850MARBL_JRA.derecho_intel.G.20260410_135953_nhg5ae.mom6.h.bgc.native.0001-01-11.nc and ERS.TL319_t232.G1850MARBL_JRA.derecho_intel.GC.20260411_092035_zdv47l.mom6.h.bgc.native.0001-01-11.nc:
-----
Could not find u10_sqr in file1!
Could not find ice_fraction in file1!

Variable: ATM_FINE_DUST_FLUX_CPL ...
... variable attribute 'units' does not match ...
'kg/m^2/s'
'kg m-2 s'

Variable: ATM_COARSE_DUST_FLUX_CPL ...
... variable attribute 'units' does not match ...
'kg/m^2/s'
'kg m-2 s'

Variable: SEAICE_DUST_FLUX_CPL ...
... variable attribute 'units' does not match ...
'kg/m^2/s'
'kg m-2 s'

Variable: ATM_BLACK_CARBON_FLUX_CPL ...
... variable attribute 'units' does not match ...
'kg/m^2/s'
'kg m-2 s'

Variable: SEAICE_BLACK_CARBON_FLUX_CPL ...
... variable attribute 'units' does not match ...
'kg/m^2/s'
'kg m-2 s'

Summary
-------
(1) Header information does not match - either variables are not the same or some variables differ in dimensions.
* 0 variables in file1 but not file2
* 2 variables in file2 but not file1
(2) Variables that matched in name and dimension differed in metadata.
(3) No differences were found in matching variables.
(4) No differences were found in missing value locations.
(5) This implies there are differences in the files.
FILES DIFFER
```