Cleanup the directory mosaic

[mlee03]

Is your feature request related to a problem? Please describe.
There are two mosaic related directories in FMS: mosaic2 and mosaic. Currently, mosaic2_mod and grid2_mod in mosaic2 are being utilized while mosaic_mod and grid_mod in mosaic have been retired. Thus the directory mosaic can/should be removed. However, the mosaic directory cannot be removed because it also contains ".c" files that are being used by mosaic2 and horiz_interp.

This issue suggests to

1. Move all ".c" files in mosaic to mosaic2 directory
2. Remove the mosaic directory
3. Clean up the ".c" files to only contain functions being used by FMS. The ".c" files seem to have been directly copied over from FRE_NCTools and many functions in those files are not used by FMS.

Describe alternatives you've considered
Leave it as it is.

Additional context
Striving to make FMS more perfect.

[rem1776]

@mlee03 That read_mosaic.c file is causing some issues for removing the macros. I was thinking it should've been ifdef'ed with fms/mpp_io as it somewhat qualifies as "old io" and uses netcdf calls directly, does that sound good to you?

We shouldn't need these io routines now since fms2_io is flawless and works as intended lol, but we've seen with create_xgrid sometimes C functions can sneak in and be used in other files without a use or anything.

We should probably bind the C functions used to a fortran routine as part of these updates.

[mlee03]

lol @rem1776 I was thinking of removing all functions in there except for get_global_area. To my knowledge, none of those read functions are used in the models

[rem1776]

@mlee03 I'll just ifdef them out for now then. #1383

[mlee03]

@rem1776 sounds good!