* yiisoft#17597, pg_constraint.consrc removed in Postgres 12
* yiisoft#17597, load schema for partitioned tables (introduced in Postgres 10)
* messed up with issue number
* #yiisoft#17597 Postgres 12 support, support GENERATED AS IDENTITY columns
* uncleared FileCache leads to falsy failures on subsequent test runs
* moved .sql for postgres 10 and 12 to separate files, added ResetSequence test for GENERATED AS IDENTITY column