Remove PG's definition of `type_cast`

All cases except for `nil` in an array have been removed. `nil` in an
array is handled by the Array type object.
Don't rely on the sql type to quote XML columns in PG
test i18n against a routed app
Merge pull request #16072 from sgrif/sg-xml-quoting

Don't rely on the sql type to quote XML columns in PG
Merge pull request #16071 from sgrif/sg-pg-type-cast

Remove PG's definition of `type_cast`
Warm up cache to prevent assertion failure.
Merge pull request #16093 from zuhao/refactor_activerecord_nested_through_associations_test

Warm up cache to prevent assertion failure.
Include fixtures to prevent foreign key violation.
Merge pull request #16094 from zuhao/refactor_activerecord_belongs_to_associations_test

Include fixtures to prevent foreign key violation.
[ci skip] Add changelog for PR #14899

The changelog entry for #14899 was missing.
Merge pull request #16095 from eileencodes/update-changelog-for-pr-14899

Add changelog for PR #14899