+Eliminate uhbt_IC and ubt_IC from restart files

  Eliminated the unused variables CS%uhbt_IC and CS%vhbt_IC from the barotropic
control structure and from the MOM6 restart files.  Also placed a logical test
for CS%Gradual_BT_ICs around all references to CS%ubt_IC and CS%vbt_IC and
eliminated these variables from the restart files when they would not be used.
Additionally some unused arguments were removed from internal subroutines and
some spelling or index case errors were corrected.  All answers are bitwise
identical, but the MOM6 restart files have fewer variables and some unused
entries in the MOM_parameter_doc files have changed.