* Move HardSigmoid to nGraph fused operators.

* UT for HardSigmoid fused operator.

* Add type_prop UT.

* Activation function parameters and hardsigmoid activation function.

* UT for lstm with hardsigmoid activation function.

* Reorder operations in implementation.

* Fix unit tests.

* Fix typo.

* Change stored activation function to pure function pointer.

* Apply style-check.

* [ONNX] Refactor LSTM tests to use NgraphTestCase

* Enable passing instance values to comparator

* Style apply.

* Fix style, syntax

* Change order of class member to fix errors.

* Switch to single-precision parameters.

* Disable unit test for IGPU.