ISPN-4574 PartitionHandling: consider less than numOwners partitions

* Merge PartitionHandlingStrategy with RebalancePolicy -> AvailabilityStrategy
* Add a stable topology with the last topology that didn't need rebalancing
* NumOwnersNodeStopInSequenceTest - stop nodes gracefully instead of abruptly
ISPN-4574 PartitionHandling: consider less than numOwners partitions
I18N for the new error messages
ISPN-4574 PartitionHandling: consider less than numOwners partitions
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