GitLab

- Verification tests that test each then/else branches for parsed IF operator
- Testing empty shape tensors for one branch -> output must be the other branch's shape
- Testing trailing 1 shape for one branch -> output must be union of both inputs

Current issue with IF operator is that we can't handle training vectors that match
in size correclty while also running into issues with empty inputs for one of the
branches for size/type checks.

* if operator support with constant condition input

* clang format

* add a missing file

* clang format

* add an onnx verifcation unit test for the if operator

* clang format'

* fix review comments

* temp version to try jenkin build

* remove unnecessary changes

* unit tests refinement for more code coverage

* clang format

* try a mutex to fix possible race condition in onnxruntime tests

* tmp changes to try jenkins build

* remove unnecessary code

* fix review comments
Co-authored-by: mvermeulen <5479696+mvermeulen@users.noreply.github.com>