Transient Replication: Add support for correct reads when transient replication is in use

Digest reads should never be sent to transient replicas.

Mismatches with results from transient replicas shouldn't trigger read repair.

Read repair should never attempt to repair a transient replica.

Reads should always include at least one full replica. They should also prefer transient replicas where possible.

Range scans must ensure the entire scanned range performs replica selection that satisfies the requirement that every range scanned includes one full replica.