Fixes for deprecation notices.

Ted Cooperrequested to merge
issue/cas_server-3621896:3.0.x-3621896-deprecation-fixes into 3.0.x
  • Future proof ConstraintValidatorInterface::validate() with void typehint.
  • Fix drupal.entityStoragePropertyAssignment in test.
  • Add PHPUnit 12 Attributes. Remove BC docblock versions.

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