Changelog (v7.1.6...v7.2.0-BETA1)

• feature symfony/symfony#54593 [PhpUnitBridge] Add ExpectUserDeprecationMessageTrait (@derrabus)
• feature symfony/symfony#57595 [Yaml] Deprecate duplicate mapping keys containing null (@xabbuh)
• feature symfony/symfony#57518 Unify how --format is handled by commands (@fabpot)