v1.17.0-beta.1: Symfony 6 compatibility

This version fixes Symfony 5.4 types deprecations and allows Symfony 6.
A minor BC break is expected if you extended some of the DBAL type methods, due to #156.

This release also adds support for Doctrine DBAL types default value on null from configuration,
as well as better support for XML/CSV denormalization of integer based enums.

Changelog

[bbc7f2e] feature #157 Allow Symfony 6 (@ogizanagi)
[f2e761a] feature #132 Support default value for generated Doctrine types (@mbrodala)
[a27eece] feature #158 Support for denormalizing XML to an integer Readable enum (@ogizanagi)
[9440cbd] minor #155 [CI] Use Flex for testing multiple Symfony versions (@ogizanagi)
[ed782a9] minor #156 Fix 5.4 deprecs & types (@ogizanagi)
[40a1a5a] minor #159 [CI] Limit mongo tests to edges checks (@ogizanagi)

Full Changelog: v1.16.0...v1.17.0-beta.1