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

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 also workaround used in pyexasol:
https://github.com/exasol/pyexasol/blob/master/pyproject.toml#L55
