Add ^12 to core_version_requirement (Drupal 12 readiness)

Andrii Podanenkorequested to merge
d12-add-caret12 into 1.0.x

Declare Drupal 12 compatibility in ws_small_y and its submodules: ^12 added, nothing dropped. The Symfony 8 return type already landed in !83 (merged).

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