Replace setuptools with Poetry

[lafrenierejm]

Description of Change

Intended to obsolete #835. This PR fixes tests and CI that are (as best as I can tell as of this writing) broken in #835.

Assumptions

Compared to the existing build system using setuptools and Pipfile, Poetry makes it easier to

• Make builds fully reproducible (especially in e.g. CI) by automating the update of the lock file.
• Ensure that pinned versions of botocore, boto3, and awscli are compatible.

Checklist for All Submissions

• [X] (NA) I have added change info to CHANGES.rst
• [X] (NA) If this is resolving an issue (needed so future developers can determine if change is still necessary and under what conditions) (can be provided via link to issue with these details):
  • [ ] Detailed description of issue
  • [ ] Alternative methods considered (if any)
  • [ ] How issue is being resolved
  • [ ] How issue can be reproduced
• [X] (NA) If this is providing a new feature (can be provided via link to issue with these details):
  • [ ] Detailed description of new feature
  • [ ] Why needed
  • [ ] Alternatives methods considered (if any)

Checklist when updating botocore and/or aiohttp versions

• [X] I have read and followed CONTRIBUTING.rst
• [X] I have updated test_patches.py where/if appropriate (also check if no changes necessary)
• [X] (NA) I have ensured that the awscli/boto3 versions match the updated botocore version