Move all Python package definitions into setup.cfg files.
A stub setup.py file remains to support `pip install --editable` it
only runs `setuptools.setup()`. The package definition is pulled from
the setup.cfg.
Each pyproject.toml file is required to specify the build system for
the given python package. In Pigweed's case so far it always specifies
Setuptools.
See this page for details:
https://setuptools.readthedocs.io/en/latest/build_meta.html?highlight=pyproject.toml#how-to-use-it
Change-Id: Ieb52ffc46b34ff1693cbfe9b95996cf9add644d1
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/54560
Pigweed-Auto-Submit: Anthony DiGirolamo <tonymd@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Reviewed-by: Wyatt Hepler <hepler@google.com>
