Fix several minor build issues

[kbattocchi]

This fixes a few build issues:

• Our nightly builds have been failing due in part to failure to properly handle the use_lkg flag in sub-workflows due to string/boolean conversions in GitHub Actions
• joblib 1.3 is not compatible with Python 3.7 on Windows
• Our package metadata includes compatible Python versions in human readable "classifier" form, but not the "requires-python" form used by tools like pip; I've addressed this by adding this field to pyproject.toml and migrating the rest of the package metadata there from setup.cfg
• We can support the new dowhy 0.10 release
• A new pycodestyle release has resulted in some new lint issues due to changes in some corner cases