Support using option `--all-extras` for poetry install

[ckunki]

Currently, PTB enables a project only to explicitly name specific extras to be installed.

notebook-connector, for example, needs to run poetry install with poetry install --all-extras.

This affects file .github/actions/python-environment/action.yml.

See

• Workaround used in pyexasol
  • Defined an extra, called "all"
  • .github/workflows/fast-tests.yml
• PTB's .github/actions/python-environment/action.yaml
• Approach used in Notebook connector