crosscluster/logical: in SHOW LDR JOBS, either report rounded down replicated time, or replicatedTimeEpoch

To ensure resumption from a cursor without data loss, the user relies on the replicated time provided by SHOW LDR JOBS. The stringified replicated time may get rounded past the persisted hlc.timestamp to the nearest microsecond. Instead, we should intentionally round down the replicated time presented in SHOW LDR JOBS, or also post the replicatedTimeEpoch (AOST) as a decimal.