Publish Python package with official action

[EpicWink]

See the Python packaging documentation, the PyPI documentation, and the official pypi-publish GitHub action documentation on trusted publishing.

Actions (click to expand)

• Configure (or use an existing) GitHub environment and add to PyPI
• In the Publish PyPi job of the Release CI workflow:
  • add aforementioned environment (eg name pypi), and permissions:

    + environment:
    +   name: pypi
    +   url: https://pypi.org/p/flatbuffers
    + permissions:
    +   id-token: write
    +   contents: read

  • in the Upload to PyPi step, switch to using the action:

    - run: python3 -m twine upload dist/*
    + uses: pypa/gh-action-pypi-publish@release/v1`

  • in the Install Dependencies step, remove twine:

    - python3 -m pip install setuptools wheel twine
    + python3 -m pip install setuptools wheel

• You will be able to remove the TWINE_TOKEN project secret

Related: #8731