feat: Support objectOverrides

[sbernauer]

Description

Part of stackabletech/issues#712
Decision: https://github.com/stackabletech/decisions/issues/64
Needs stackabletech/documentation#807 for the documentation part

The actual code change is oversee-able, most of the added lines are tests.

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

[Techassi]

Mostly lgtm, a few various question, comments and suggestions.