Currently TextLine field type does not normalize (downcase) sortKey for the Persistence, causing failure when using search with PostgreSQL.

Ref: https://github.com/ezsystems/ezpublish-kernel/pull/514

FieldType should downcase sortKey for the persistence value. In the existing field types that is done with PHP's strtolower function, but in the LS it is done using TransformationProcessor which is for the new kernel reimplemented in the Legacy Storage.

Therefore TransformationProcessor needs to be moved out of Legacy Storage and all field types need to use it for sortKey normalization.