*  WIP graph pass to lower ngraph to ngraph dialect

* resolved compiler errors

* - refactor ngraph-dialect to graph pass

* - fix compilation issue
- unit test passes

*  - style fix

* Addressed PR comments

* - move NgDialectConversionPass to anonymous namespace

* - use getModule() to access module inside the graph pass
- address PR comments

*  - fix failing unit test case for negative padding
- make builder as an object isntead of pointer to an object

* Address PR Comments