onnxruntime

Load checkpoint in cpp (#12352)

* Load checkpoint in cpp

* removed unused imports

* throw error on invalid name and change function name

* inplace model assignment, change name and other comments resolved

* name change  on import

* Addded unit test, resolved comments

* remove unused  imports

* resolved comments

* refactoring too reduce memoory allocation

* resolved extra comments

* changed files hierarchy an force added onnx moodel

* solved order of function argument

* used gtest macros on test cases

Co-authored-by: Adam Louly <adamlouly@microsoft.com@orttrainingdev7.d32nl1ml4oruzj4qz3bqlggovf.px.internal.cloudapp.net>