Rename `Operator` to `ControllerManager` in v5

[csviri]

Operator pattern consists of (Custom)Resources accessed by API Server and Controllers. When we implement in java part is just the controller part, more of the possibly bundled together. In fact the Operator should be called something that resembles this, like ControllerManager (in go it is called Manager).

(I don't remember exactly why we named it Operator at the beginning of the project, but this might be confusing)

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[github-actions]

This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 14 days.

[github-actions]

This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 14 days.

[metacosm]

Personally, I don't think that we should change this at this point. It might not have been the best term for sure but I don't see any value in changing the name now just for the sake of it. It won't help existing users and it will require us to rewrite significant parts of the code and documentation, so I'd be in favor of just leaving this as-is.

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This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 14 days.