Investigate new method of determining Poetry development dependencies

With #991 it came to our attention that with the more recent Poetry lock file changes (see https://github.com/python-poetry/poetry/blob/master/CHANGELOG.md#150---2023-05-19) the category field is no longer present.

This was being used to determine whether a dependency was used in the main package or as a development only dependency. Investigate a new method of determining which dependencies are used for development only as the detector will now be overreporting.

Start by reviewing issue #991 and the Poetry 1.5.0 changelog entry about lock file changes, then inspect the Poetry lock-file dependency handling in this repository. Done means the detector can identify development-only dependencies without relying on the removed category field and no longer overreports them.

Written by the indexing model from the issue text.