* Add builder for {de}quantize

* Add declaration in header

* Add mkldnn support for {de}quantize

* Add support for {de}quantize with mkldnn

* Add Dex support

* Generalizing some api's and adding a test case for DQ in backend_test.in.cpp

* Unify scale between ngraph and mkldnn

* Check for nullptrs

* PR feedback

* fix unit test failure

* Adding tests for builder and deleting the backend tests

* curly braces

* test rename