Convert "Version" types to "str" outside of validation

[ThomasLaPiana]

Closes #

Description Of Changes

The clever (not so much apparently) Version type I created is causing issues with database insertion over in Fides ([PR}())

This uses the version during validation but otherwise treats it as a string. This will be released immediately as Fideslang version 2.0.1

Code Changes

• add version validation while storing as strings
• add new tests to validate empty values on instantiation

Steps to Confirm

• list any manual steps taken to confirm the changes

Pre-Merge Checklist

• All CI Pipelines Succeeded
• Issue Requirements are Met
• Update CHANGELOG.md

[adamsachs]

lgtm! 👍 just a small comment for curiosity's sake, not suggesting you need to make the update here.