Implement hetfrz tuning factors modifications for Oslo Aero as tested in Key-Clim cloud2 experiments

[gold2718]

Implement the KeyClim cloud2 modifications, recently introduced in the noresm2_3_develop branch.
The implementation requires one difference:
Replace hetfrz_aer_scalfac with hetfrz_bc_scalfac and hetfrz_dust_scalfac to allow for better tuning of dust and black carbon.

[oyvindseland]

Edited title since it is only one of the parameters that was changed in KeyClim cloud2