[ENG-9692] upgrates part 1: pyproject.toml + poetry

[aaxelb]

• replace setup.py with pyproject.toml
• use poetry for dependencies and packaging
• stop testing python <3.8 and django <3.2 (will add more recent versions in next pr)

note: github actions hasn't been running on this repo -- verified tests pass with py3.10 and dj4.1; will require passing tests on full version ranges (up to latest) before merging feature branch to main