Persist user-defined core properties

CREATE collection and ADDREPLICA commands both accept core properties (as property.* parameters) that are then added to the core.properties file. However, those additional properties are not persisted anywhere in the cluster state.

Consequently, cores that are added later to a collection (e.g., by adding a new replica) do not contain those properties, which seems inconsistent. I would like to be able to specify a core property when creating a collection, and not repeat myself when adding a new replica later on.

It might be a breaking change if people do not expect this behaviour though.

Related to SOLR-16305.