Require Official Python Plugins to be valid Python Packages

[mfleader]

Please describe what you would like to see in this project

Ensure that the given plugin is a valid Python plugin.

1. has pyproject.toml
2. has a directory at root or under a root src directory that has the same filename in the pyproject.toml at the pyproject.project.name, or tool.poetry.name, key values.

Please describe your use case

This is to enforce some similarity in the directory structure of our Python plugins, and to facilitate publishing them to a public Python package repository, like pypi.