🚀[FEA]: Save NetCDF4 timedelta units compatible with xarray

[swbg]

Is this a new feature, an improvement, or a change to existing functionality?

Improvement

How would you describe the priority of this feature request

Medium

Please provide a clear description of problem you would like to solve.

The NetCDF4 IO backend saves timedelta units as "h", "s", etc., while xarray only automatically decodes units "hours", "seconds", etc. Both versions seem to be acceptable according to CF conventions but it would be convenient to use xarray-style units

See here, where units are set according to numpy convention: https://github.com/NVIDIA/earth2studio/blob/main/earth2studio/io/netcdf4.py#L135
See, e.g., here, where xarray docs state they are using long-form units: (at the bottom, decode_timedelta) https://docs.xarray.dev/en/stable/generated/xarray.decode_cf.html
See here, in the xarray code: https://github.com/pydata/xarray/blob/main/xarray/coding/times.py#L80

Current workaround:

ds = xr.open_dataset("./output.nc", engine="netcdf4")  # some forecasting output
# lead_time has dtype int64
ds.lead_time.attrs["units"] = "hours"  # instead of "h"
ds = xr.decode_cf(ds)
# lead_time has dytpe timedelta64