MCR-3642 Do not require fixed classname properties for implicit classes in collections

[toKrause]

Link to jira.

Pull Request Checklist (Author)

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Ticket & Documentation

• The issue in the ticket is clearly described and the solution is documented.
• Design decisions (if any) are explained.
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Testing

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Multi-Repo Considerations

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[toKrause]

rebased to current version of main