feat(stackable-versioned)!: Automatically generate conversion roundtrip tests

[sbernauer]

Description

This was originally implemented back in #1050, but was removed to keep things simpler.

As I spiked a CRD conversion in secret-operator I wondered if my implementation was actually roundtrip-safe. So I remembered this follow-up task and re-added the testing infrastructure. Now the compiler will force me to find out if it is roundtrip-safe 🚀

The PR adds some testdata for all stackable-operator structs. It unsurprisingly uncovered the missing roundtrip-ability of the Person test-struct, as it changes a field, while so far only field additions are supported by the conversion tracking. I hope we don't have a CRD conversion that fails roundtrips in production yet :) This PR is here to prevent exactly that.

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

Author

• Changes are OpenShift compatible
• CRD changes approved
• CRD documentation for all fields, following the style guide.
• Integration tests passed (for non trivial changes)
• Changes need to be "offline" compatible

Reviewer

• Code contains useful comments
• Code contains useful logging statements
• (Integration-)Test cases added
• Documentation added or updated. Follows the style guide.
• Changelog updated
• Cargo.toml only contains references to git tags (not specific commits or branches)

Acceptance

• Feature Tracker has been updated
• Proper release label has been added