cam6_4_074: Complete CCPPization of Hack shallow convection

[jimmielin]

Purpose of changes (include the issue number and title text for each relevant GitHub issue):

• Convert Hack shallow convection and move to atmospheric_physics (Convert Hack shallow convective scheme to CCPP and move to atmospheric_physics #1174)

Other changes for CCPPization that resolve issues in atmospheric_physics:

• ZM convective mass flux (atmosphere_convective_mass_flux_due_to_deep_convection) units inconsistent with snapshot (ZM convective mass flux (atmosphere_convective_mass_flux_due_to_deep_convection) units inconsistent with snapshot atmospheric_physics#197)
• Add errmsg, errflg to cloud_fraction_fice_run (Add errmsg, errflg to cloud_fraction_fice_run atmospheric_physics#201)

List all existing files that have been modified, and describe the changes:

M       .gitmodules
M       src/atmos_phys
   - update atmospheric_physics to bring in Hack shallow convection,
     and related CCPPized physics changes.

M       bld/configure
   - add path to atmos_phys/schemes/hack_shallow

M       src/physics/cam/convect_shallow.F90
M       src/physics/cam/hk_conv.F90
   - CCPPize Hack shallow convection.


M       src/physics/cam/vertical_diffusion.F90
M       src/physics/cam/physpkg.F90
M       src/physics/cam7/physpkg.F90
   - removal of unused second dimension (pcnst) of qpert because it is not supported
     in CAM-SIMA snapshot reads.

M       src/physics/cam/macrop_driver.F90
M       src/physics/cam/zm_conv_intr.F90
M       src/physics/cam/rk_stratiform.F90
   - add errmsg, errflg to cloud_fraction_fice CCPPized scheme.

M       src/physics/cam/zm_conv_intr.F90
   - move unit conversion of convective mass fluxes to kg m-2 s-1 to 
     inside CCPPized scheme for consistency with snapshots.

[nusbaume]

Good work @jimmielin! I just had a few minor change requests.

[nusbaume]

Everything looks great to me now. Thanks @jimmielin!