Remove regridding funcs that are in ClimaUtilities

[imreddyTeja]

Closes #1107
Regridder module removed. The hdwrite_regridfile_rll_to_cgll only works for 2d spaces in ClimaUtilities, and the function in Regridder.jl also worked for 3d spaced, so this functionality is lost.

The functions read_available_dates and yyyymmmddd_to_datetime are copied from ClimaUtilities. This is necessary because land_fraction needs the first date in the dataset. TempestRegridder calls hdwrite_regridfile_rll_to_cgll, which extracts the dates and returns them, but TempestRegridder then discards those extracted dates.

The regridder functions in ClimaUtilities do not work properly when the time dim is made up of numbers, and it errors when the time dim is made up of large floats. To function properly, the time time must be datetimes. The functions in Regridder.jl worked with the time dim as numbers.

Many of the regridding functions in Regridder.jl allowed the outfile_root to be set. When using the TempestRegridder, it is autmatically set to the varname. This results in file with names structured like: "varname_varname_time.hdf5"

Purpose

To-do

• move Regridder module docs to news.md
• make changes in ClimaUtilities (time reading, outfile_root, varname to varnames)
  see here
  changes to the time reading probably require a small discussion, and making TempestRegridder support multiple varnames requires enough changes to be a separate issue (implementing would change interface, or would need to continue supporting old interface)
• Docs differentiate internal vs external functions
• test for binary mask

Content

• Regridder module removed (also checked that there is equivalent functionality in ClimaUtilities. If there was not, it is noted)
• added to NEWS.md

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• I have read and checked the items on the review checklist.