Refactor test to use DdlHelper.

Follow-Up to https://github.com/rails/rails/pull/14400

This ensures that all tables are removed after each test and thereby
allowing us to run the tests in a random order.
Require yaml explicitly
Merge pull request #14474 from tgxworld/table_cleanup_after_each_test

Refactor test to use DdlHelper.
No need to call to_sym

It is already called inside type_to_sql method.
fix bug on non empty defaults for pg array columns

fixes #10613
Merge pull request #14528 from planas/patch-1

Require yaml explicitly on #database_configuration
fix mysql builds
Merge pull request #14509 from lukesteensen/pg-array-defaults

remove calls to sql_type on pg columns
Tiny doc fix for Strong Parameters

- accepts_nested_attribute_for -> accepts_nested_attributes_for
Merge pull request #14535 from iancanderson/patch-1

Tiny doc fix for Strong Parameters