add ability to override python version

[cfhammill]

Intent

I am unable to deploy to connect from my development server because the python I'm using is newer than the versions available on connect. I would like to be able to tell rsconnect-python to use a different python version, so I patched in that feature.

Type of Change

• [x] Bug Fix
• [x] New Feature
• [ ] Breaking Change

Approach

This PR modifies the environment detection code to add an override option where the Environment object is cloned with the updated python version. This was weaved out to the CLI.

Automated Tests

No tests written, would like feedback on idea / style / etc. before adding tests. Someone more familiar with the project could also provide direction for testing this feature.

Directions for Reviewers

Try deploying something and using --override-python-version <version> or -op <version>

Checklist

• [ ] I have updated CHANGELOG.md to cover notable changes.
• [ ] I have updated all related GitHub issues to reflect their current state.