With this patch, SHOW VIRTUAL CLUSTER ... WITH REPLICATION STATUS will display
the replication lag.

Fixes cockroachdb#120647

Release note (sql change): SHOW VIRTUAL CLUSTER ... WITH REPLICATION STATUS now
displays the PCR replication lag.

Epic: none

Release note (sql change): This patch refactors the output of SHOW VC WITH
REPLICATION STATUS to 1) remove the replication_job_id, service_mode return
fields; 2) reorder to following columns to: retained_time, replicated_time,
replication_lag, cutover_time; 3) rename the data_state field status and moves
to the last return column.