[ONNX] Extend converter for Attention from Microsoft onnxruntime contrib opset (#13797)

* add type & shape checking

* add base class for Attention converter

* add support for 'past' input

* add support for 'unidirectional' attribute

* fix for 'huggingface implementation'

* add common method for calculating Attention

* expand test coverage for Attention

Author: KJlaccHoeUM9l