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
Do not overwrite selected and disabled attributes
Fix polymorphic preloads on NOT NULL _type columns.

Defer to Association#klass instead of having a custom/duplicate code.
Merge pull request #14509 from lukesteensen/pg-array-defaults

remove calls to sql_type on pg columns
Simplify Preloader#grouped_records code.

The new method relies on AR::Associations::Association knowing about both reflection and a model class.

AR::Base#association now raises a descriptive error when trying to access non-existent associations. Previously it would blow up with a confusing NoMethodError: undefined method `association_class' for nil:NilClass.
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
refactor, put `PostgreSQLColumn` into `column.rb`.

We have `connection_adapters/column.rb` so it's easier to remember
that the column in in a separate file.
Merge pull request #14532 from thedarkone/polymorphic-preload-fix

Fix polymorphic preloads on NOT NULL _type columns
Fix release task

Add a parentheses.
related: b4c96490eeb1fbb944e116c7703dd528b37fc08a
Merge pull request #14542 from arthurnn/fix_release_task

Fix release task
Add test for selected and disabled custom attributes in options_for_select
Merge pull request #14539 from lparedes/master

Do not overwrite selected and disabled attributes
add capture_sql method to compare sql statements and compare

Other methods compare specific patterns, this method outputs
the actual sql query that is generated.