PostgreSQL database driver (#5861)

* [test/database/list] Fix test list 4 being used in two different tests

* [database/postgres] PostgreSQL database driver

* [database/postgres] Make transactions work based on continuation scope.

* [database/postgres] Implement nested transactions

* eslint --fix

* Add database changes from earlier this week to the PostgreSQL driver.

* Fix typo

* Fix postgres.incrObjectFieldBy returning undefined instead of null when given NaN

* [database/postgres] Fix sortedSetsCard returning an array of strings.

* Update socket.io postgres adapter

* Fix PostgreSQL erroring when multiple updates are made to the same sorted set entry in a single operation.

Add a test case to catch this error.

* Fix lint errors.

* Only prune sessions on one instance in a cluster to avoid deadlocks.

They're caught and handled by the database server, but they spam the logs.

* Fix arguments.slice.

test/database.js

@@ -48,6 +48,11 @@ describe('Test database', function () {
 					assert.equal(err.message, 'The `mongodb` package is out-of-date, please run `./nodebb setup` again.');
 					done();
 				});
+			} else if (dbName === 'postgres') {
+				db.checkCompatibilityVersion('6.3.0', function (err) {
+					assert.equal(err.message, 'The `pg` package is out-of-date, please run `./nodebb setup` again.');
+					done();
+				});
 			}
 		});
 	});