Multi-level container registry images

What does this MR do?

Adds support for multiple container images under the same project/group namespace.

Example: registry.example.com/group/project/any/image-name:optional-tag

Screenshots

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug

Credits

Originally contributed by @andrebsguedes in !7154 (closed).

What are the relevant issue numbers?

Closes #17801 (closed)