Changelog (v7.2.6...v7.3.0-BETA1)

• feature symfony/symfony#52749 [Serializer] Add discriminator map to debug commmand output (@jschaedl)
• feature symfony/symfony#59828 [Serializer] Add defaultType to DiscriminatorMap (@alanpoulain)
• feature symfony/symfony#58488 [Serializer] Fix deserializing XML Attributes into string properties (@Hanmac)
• feature symfony/symfony#59670 [Serializer] Add NumberNormalizer (@valtzu)
• feature symfony/symfony#59641 [Serializer] register named normalizer & denormalizer aliases (@mathroc)
• feature symfony/symfony#58599 [Serializer] Add xml context option to ignore empty attributes (@qdequippe)
• feature symfony/symfony#59286 [Serializer] Deprecate the CompiledClassMetadataFactory (@mtarld)