onnxruntime

Serialize optimized onnx model (#1470)

* Model serialization

* Removed duplicate symbol

* Minor update

* Review comments

* add tests

* Model serialization

* Removed duplicate symbol

* Minor update

* Merged PR 1106437: Model Serialization in onnxruntime

* Review comments

* Merged PR 1107226: Review comments

Review comments

* add tests

* Fixed merge conflict

* Correct python tests

* InferenceSesssion Refeed Test

* Replace use of widechar const literal-L

* Fixed failing tests

* Updated comment

* Removed unnecessary session options

* Spell check on comments

* Do not serialize when level 3 optimization specified

* Updated error logs

* Changed log severity to WARN