ETKF and var4d clean up

Replace AWS ERA5 with Google Cloud Storage ERA5 (#45)

* Add dependencies to pyproject.toml

* Remove environment.yml

* Replace from jax.config import config (deprecated) with just jax.config

* Streamline resources and xarray manipulation to match new versions

* Call asnumpy on xarray ds when opening to avoid scipyarraywrapper attribute error

* Replace jax.numpy in1d (no longer exists) with isin

* Update getargspec (deprecated) to inspect.signature

* Add qgs to pyproject.toml

* Fix mistake, signature() must called on h

* Add zarr, dask, and others needed for google cloud downloads

* Need to precompute indexer when using ds.where on remote zarr array

* Add qgs and cloud to dev install (will add pyqg later)

* Move from conda to pip for CI testing

* Rename CI config yml from conda to pip

* Add flake8 to dev build

* Use workaround for installing pyqg with older Cython

* Manually install wheel before pyqg install

* Add dask for cloud build

* Remove pyqg from dependencies for now, include tests in full install

* ETKF fix to exclude end of timewindow exact match observations

* Add extras to example build (ray, pandas, matplotlib)

* Add hyperopt to examples build

* Add cftime to examples (needed for loading netcdf)

* Update gcp to use analysis ready zarr. Working but seems quite slow

* Change defaults to match aws

* Remove AWS

* Remove aws tests

* Updated gcp tests and replacing aws with gcp in observer tests

* Streamline xarray dataset import

* Rmeove typo in gcp docstring

* Remove pyqg from tests if not installed

* Skip barotropic tests if pyqg not installed

* Convert xarray ds to numpy to avoid data errors

* Make cftime a base dependency

* Only run pyqg observer test if pyqg is installed

Improved dimensions/coordinates handling for NetCDFs and Zarrs (#27)

* Sort latitude descending

* decode_coords=all to remove bnds from data_vars

* Add include_vars and exclude_vars

* Make lat_sorting an arg for load_netcdf, defaults to descending

* Handle data_vars with different dims

* Automatically handle unrecognized dimensions

* Print shapes in data var shape warning

* Better formatting for variable shapes in warning