Import Hashables from collections.abc (and mostly fix the CI)

[gabrieltseng]

• Fix bug described in Google Colab: AttributeError: module 'collections' has no attribute 'Hashable #118
• Increment action versions, and remove coverage for python 3.6
• Remove CI for python 3.7 on mac due to Python 3.7 recently broken (no _bz2 module) on macOS 13 actions/setup-python#682)
• Update CI to include tests for python 3.10
• For windows, install h5py using conda (due to DLL load failed h5py/h5py#1774 when installing from pip)
• Remove learn2learn as a dependency, since it depended on gym which no longer works with setuptools
• Pin xarray and pandas due to breaking changes (a future TODO is to update those packages)
• Reformat code using latest version of black