Add support for Symfony Language Constraint

manual test case:
add a Language constraint to field_test, Alpha3 uncheck, save it.

if populate field_test "123456", get an error message.

if populate field_test "en", no error message.

Note:

You need install symfony/intl and PHP's intl extension, to make this constraint works.
composer require symfony/intl

Automatically closed - issue fixed for 2 weeks with no activity.