[CORE] Try to correct 'undefined' and 'dynamic' type serialization

[EgorDuplensky]

Details:

• There is misalignment between ov::element::type string serialization / de-serialization methods
  and the ir serializer itself.
  After introduction of internal opset FullyConnected operation the 'undefined' element type basically
  became valid and serializable
• Try to update the serializer and see which tests are going to fail
• There are potential issues with IR backward compatibility which should be addressed carefully

[EgorDuplensky]

@praasz @slyalin @itikhono FYI