[Enhanced Monitoring] pglogical.show_subscription_table

[vjeeva]

Is your feature request related to a problem? Please describe.
It would be nice to extract all the table sync info from pglogical when running replication, to see if table copies have finished, replication level, etc. Seems pglogical.show_subscription_table is the command to run.

Describe the solution you'd like
An extra view with all tables in the subscription listed, along with their sync status and level.

Describe alternatives you've considered
N/A, we have no insight into this right now.

Additional context
DMS shows this on a per-table level too. We need this!

[vjeeva]

database=> SELECT pglogical.show_subscription_table('pg1_pg2', 'some_table');
            show_subscription_table
-----------------------------------------------
 (public,some_table,replicating)

[vjeeva]

During the initializing COPY phase, we see unknown above. We should also track table sizes in the destination against the source, and also have a column for that table replication status (unknown == initial copy it seems).

[vjeeva]

Note that this command must be run on the destination database.