Cedar-backup3

* Drop support for Python 3.7.
* Rename CREDITS -> NOTICE for consistency with my other Python projects.
* Migrate release.py and various help output to use importlib.metadata.
* Convert to standard version of .run/tasks/release.sh used elsewhere.

* Support Python 3.11.
* Use locale.getlocale() instead of .getdefaultlocale() for Python >= 3.11.
* Adjust GHA build to run MacOS and Windows tests only on latest Python.

* Remove execute bit from amazons3.py and span.py for Debian policy.

* Refactor the run script and pre-commit hooks to reduce duplication.
* Rework the GitHub Actions build process to pull out shared code.

* Upgrade to Poetry v1.2.0 and make related build process changes.
* Upgrade to Pylint v2.15.0 and address warnings.
* Fix Pylint's configured class-attribute-naming-style to be snake_case.
* Adjust Black configuration to target Python 3.7, 3.8, 3.9, and 3.10.
* Add dependency caching to GitHub Actions workflow.
* Fix the GitHub Actions matrix build to properly target Windows and MacOS.
* Fix problems with test suite under Windows when running in GitHub Actions.
* Update various dependencies for the developer environment.

* Adjust the pyproject.toml include directive to limit what goes into wheel.
* Remove the Safety scanner from the pre-commit hooks and GitHub action.