v23:
Split pg_set_relation_stats into two functions: pg_set_relation_stats with named parameters like it had around v19 and pg_restore_relations_stats with the variadic parameters it has had in more recent versions, which processes the variadic parameters and then makes a call to pg_set_relation_stats.
Split pg_set_attribute_stats into two functions: pg_set_attribute_stats with named parameters like it had around v19 and pg_restore_attribute_stats with the variadic parameters it has had in more recent versions, which processes the variadic parameters and then makes a call to pg_set_attribute_stats.
The intention here is that the named parameters signatures are easier for ad-hoc use, while the variadic signatures are evergreen and thus ideal for pg_dump/pg_upgrade.
rebased to a0a5869a8598cdeae1d2f2d632038d26dcc69d19 (master as of early July 18)