Required updates to MALI ISMIP6 forcing files and their use in run test case

[matthewhoffman]

In compass/landice/tests/ismip6_run/ismip6_ais_proj2300/set_up_experiment.py, it is assumed the SMB forcing file is named processed_SMB_*_smbNeg_over_bareland.nc, because the forcing files used at the time of our formal ISMIP6-2300 runs used that naming convention. However, the ISMIP6 forcing test case was subsequently adjusted to use the naming convention:

f"{mali_mesh_name}_RACMO2.3p2_ANT27_smb_climatology_1995-2017.nc"

(https://github.com/hollyhan/compass/blob/867bab78c3b8af109069c571acc9c87a02885fe3/compass/landice/tests/ismip6_forcing/atmosphere/process_smb_racmo.py#L53-L54)

If the ISMIP6 run test case is used in the future with newly generated forcing files, the naming convention will need to be corrected in the run test case.

This also applies to the TF forcing files set up by the run test case (tf_search_path).

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Also, in the actual ISMIP6 experiments we applied large negative SMB anywhere there was bare ground in the initial condition to prevent advance of ice onto unglaciated bare land in the simulations. The adjustment to the SMB field was done manually. This adjustment should be added in to the generation of the SMB files in the ISMIP6 forcing test case.