Modernize integration with Doctrine internals

This 3.0.0 release improves the integration with Doctrine internals and adds support for type-safe TranslatableInterface fields.

Unless you extend classes that were meant to be internal to this bundle and never used as extension points (see #23), you should be able to upgrade without further ado.

What's Changed

• Update test matrix for PHP 8.1 and above, Symfony 6.4 and above by @mpdude in #20
• Mark classes internal to this bundle as final by @mpdude in #23
• Make members private instead of protected, where possible by @mpdude in #24
• Use PHP 8.1+ language features by @mpdude in #25
• Improve test code style by @mpdude in #27
• Improve and simplify integration with ORM internals by @mpdude in #28
• Test that Translatables can be used for values beyond strings, e. g. objects by @mpdude in #30
• Show that new translations can be persisted by @mpdude in #29
• Add support for type-safe TranslatableInterface fields (Case 167550) by @mpdude in #31

Full Changelog: 2.5.0...3.0.0