Fv3config

-------------------

Bug fixes:
~~~~~~~~~~
- ensure that empty assets "" are not downloaded
- work around an an upstream bug where fsspec.walk yields empty strings as filenames
- when a coupler.res file is present in the initial conditions, the base date in the
diagnostics table is now set to the initialization date rather than the current date,
ensuring reproducible restarts in segmented runs.

Breaking changes:
~~~~~~~~~~~~~~~~~
- when using a directory of restart files as an initial condition -- as opposed to a
bridge between segments -- it is now required to set the ``coupler_nml.force_date_from_namelist``
parameter to true, and set the ``coupler_nml.current_date`` parameter to the intended
start date of the simulation.

License changes:
~~~~~~~~~~~~~~~~
- fv3config is now released under an Apache 2.0 license rather than a BSD license,
as this is the preferred license for software released by the Allen Institute for
Artificial Intelligence.

-------------------

Breaking changes:
~~~~~~~~~~~~~~~~~
- rename ``fv3config.update_config_for_nudging`` to ``fv3config.enable_nudging`` and make this function return a new config instead of mutating the input
- rename ``update_config_for_nudging`` command line entrypoint to ``enable_nudging``

Bug fixes:
~~~~~~~~~~
- ensure ``fv3config.write_run_directory`` does not mutate input config
- fix bug in which ``DiagTable.from_str`` failed on lines that contain only whitespace

Minor changes
~~~~~~~~~~~~~
- The responsibility of retrying gcsfs operations is now delegated to gcsfs.

-------------------

Bug Fixes:
~~~~~~~~~~
- replace a couple instances of yaml.dump/load with fv3config.dump/load

-------------------

Breaking changes:
~~~~~~~~~~~~~~~~~
- Modify the serialization APIs
- add ``fv3config.load/dump``
- remove ``fv3config.config_to_yaml`` and ``fv3config.config_from_yaml``

Bug Fixes:
~~~~~~~~~~
- use ``DiagTable`` aware serialization routines inside the CLIs

-------------------

Minor changes:
~~~~~~~~~~~~~~

- don't specify a consistency in the `fsspec.filesystem` instantiation

-------------------

Major changes:
~~~~~~~~~~~~~~

- add `DiagTable` class with associated `DiagFileConfig` and `DiagFieldConfig` dataclasses.
- make `fv3config.config_to_yaml` a public function.
- update `fv3config.config_to_yaml` and `fv3config.config_from_yaml` to go between
`fv3config.DiagTable` and `dict` types as necessary when serializing/deserializing
- `write_run_directory` provisions necessary `patch_files` for config if the
`fv_core_nml.nudge` option is set to `True`.