Reinitialize should allow to override existing config in collationGeneration (#4833)

Currently the `Initialize` and `Reinitialize` messages in the
collationGeneration subsystem fail if:
-  `Initialize` if there exists already another configuration and
- `Reinitialize` if another configuration does not exist

I propose to instead change the behaviour of `Reinitialize` to always
set the config regardless of whether one exists or not.

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Co-authored-by: Bastian Köcher <[email protected]>
Co-authored-by: Andrei Sandu <[email protected]>