Feat: Customization of topology relationships

### What would you like to be added?

Support customization of topology relationships between different GVKs
Currently it is managed in a relationship.yaml

### Why is this needed?

Admins should be able to customize relationship definitions especially for CRs

Start by reading relationship.yaml and trace where its topology relationship definitions are loaded and applied. Define how administrators would customize relationships between different GVKs, especially custom resources, and verify that customized definitions are used consistently.

Written by the indexing model from the issue text.