Python: Improve project setup and test runner conveniences after unboxing. Add CI configuration. Prepare packaging.

[amotl]

About

• Use vanilla setuptools-based pyproject.toml instead of Poetry
• Improve setup_grammar.py grammar compiler/generator
• Make project setup and running software tests self-contained
• Improve documentation
• Add CI configuration for software tests and Dependabot

Details

I think Poetry will only be needed for larger or more complex projects. For a project like this, I think a vanilla setuptools-based pyproject.toml will be enough.