New IC files for clm45/clm50 coupled cases, add 2010 compset

Improve logic for picking initial condition files (finidat). Add new finidat files
for when coupled to CAM (LND_TUNING_MODE=clm*_cam6.0) for both 1850 (from CMIP6 B1850 case)
and 2000/2010 (from CMIP6 BHIST case).

Logic for picking finidat files now will pick a finidat file that it interpolates from
provided the default settings allow use_init_interp to be true. This makes it more likely
to pick a file to startup from if at all possible, rather than dying with an error that
a finidat couldn't be found (which the user could override to get the new behavior by adding
use_init_interp=T to their user_nl_clm).

In namelist settings for finding finidat files for sim_yr=2000, be explict on which tuning mode
is being matched and duplicate the clm4_5/clm5_0 GSWP3v1/CRUv7 matches. This gets it to match
the correct ones and allows them to be distinquished in the future.

Added CLM_NML_USE_CASE=2010_control, and settings for sim_yr=2010, which is needed for some new CAM compsets.