Use importlib_metadata for <3.10 compatibility

[Ariana-B]

Reason for this pull request

#1468

Proposed changes

• Replace entry_points(group=group) with entry_points().select(group=group) for python <3.10 compatibility

• Closes python 3.8/3.9 doesn't support entry_points with either group or select #1468

• Tests added / passed

• Fully documented, including docs/about/whats_new.rst for all changes

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📚 Documentation preview 📚: https://datacube-core--1469.org.readthedocs.build/en/1469/

[codecov]

Codecov Report

Patch coverage: 50.00% and project coverage change: -0.02 ⚠️

Comparison is base (5fed4a6) 91.77% compared to head (cef49eb) 91.76%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1469      +/-   ##
===========================================
- Coverage    91.77%   91.76%   -0.02%     
===========================================
  Files          132      132              
  Lines        14537    14540       +3     
===========================================
+ Hits         13341    13342       +1     
- Misses        1196     1198       +2     

Impacted Files	Coverage Δ
datacube/drivers/driver_cache.py	93.10% <50.00%> (-6.90%)	⬇️

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[omad]

I've tested this on Python 3.9 and it doesn't work, that select() functional also doesn't exist yet.

The Compatibility Note on https://docs.python.org/3/library/importlib.metadata.html is not clearly written.

The behaviour in Python < 3.10 is to return a dictionary keyed on group, so we could use:

>>> entry_points()['datacube.plugins.index']
(EntryPoint(name='default', value='datacube.index.postgres.index:index_driver_init', group='datacube.plugins.index'), EntryPoint(name='memory', value='datacube.index.memory.index:index_driver_init', group='datacube.plugins.index'), EntryPoint(name='null', value='datacube.index.null.index:index_driver_init', group='datacube.plugins.index'), EntryPoint(name='postgis', value='datacube.index.postgis.index:index_driver_init', group='datacube.plugins.index'))

But the Compatibility Note warns that will break in the future.

I think the simplest/best option is to add an optional dependency importlib_metadata>=3.6; python_version<3.10. See Dependencies Management in Setuptools.

[omad]

That should both be reliable in the future, and doesn't rely on adding extra code for handling different return types in different python versions/importlib.metadata versions.

[emmaai]

Thanks!