[Symfony 6] Add "array|string|int|float|bool|\ArrayObject|null" to all Normalizer classes that implement the method ::normalize()

Problem/Motivation

Method "Symfony\Component\Serializer\Normalizer\NormalizerInterface::normalize()" will return "array|string|int|float|bool|\ArrayObject|null" as of its next major version.

This deprecation warning is given by Symfony 5.4 that in Symfony 6 the return value must be of the type: array|string|int|float|bool|\ArrayObject|null. The problem is that in Drupal's implementation we are returning an instance of the class Drupal\jsonapi\Normalizer\Value\CacheableNormalization, which is not one of the allowed return types.

Proposed resolution

TBD

Remaining tasks

TBD

User interface changes

None

API changes

TBD

Data model changes

None

Release notes snippet

TBD