- Remove the replication_factor.replication_factor() in favor of
usize::from(replication_factor) to make the conversion more explicit.
- Implement Display on ReplicationFactor so that it can be formatted
without converting to usize
- Use ReplicationFactor in the constructor of LayoutVersion and add a
method to get a ReplicationFactor from a LayoutVersion, despite
LayoutVersion still storing it as usize internally.