feat!: Add conversion webhook

[sbernauer]

Description

Part of https://github.com/stackabletech/issues/issues/642 Needs https://github.com/stackabletech/operator-rs/pull/1066

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.
• [ ] Helm chart can be installed and deployed operator works
• [ ] Integration tests passed (for non trivial changes)
• [ ] Changes need to be "offline" compatible
• [ ] Links to generated (nightly) docs added
• [ ] Release note snippet added

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
• [ ] Links to generated (nightly) docs added
• [ ] Release note snippet added
• [ ] Add type/deprecation label & add to the deprecation schedule
• [ ] Add type/experimental label & add to the experimental features tracker