Refresh database tables when we see a relation message in the replication slot

[acco]

We should be using the presence of relation messages coming through the replication slot as a possible signal that schemas have changed. If schemas change, we should trigger a refresh of the PostgresDatabase.tables

Easiest to start: When we see an unrecognized table coming through the slot, good sign something was created.

Will help in test/dev, where tables may be getting dropped/created frequently