General cleanup of surface.F90 needed

[LarissaReames-NOAA]

Similar to Issue #504 , the entire file surface.F90 could use some clean up. Outside of the interp subroutine, there's some old code in there that's no longer used, and an opportunity in nst_land_fill to move to using a loop over a FieldBundle to do most of the work of that subroutine. As this won't involve adding any functionalities that aren't already there, but mostly will be removing old code, I don't anticipate many tests being needed. A short test could probably be used to check that the newly-modified nst_land_fill is properly filling land points with the expected values.