Adding Poetry for better dependency and build management

This is an initial pass at adding Poetry as a dependency and build management tool to improve how version pinning, locking, and dependency resolution are managed.

Merge Request Checklist

• Link to an issue
• Include the proposed fix or feature
• Include and update tests for the modified code
• Include a documentation change
• Add a CHANGELOG.md entry in the Unreleased section

Once your merge request is complete, please assign it a Meltano maintainer for review cycle. Once the review cycle finished, the reviewer shall approve the merge request so it can be merged by any Meltano maintainer.

Closes #2367 (closed)