onnxruntime

fix transformer model unit tests (#14319)

For following failures, folder of convert_to_onnx should be specified to
import for source code case:
FAILED
test_gpt2_to_onnx.py::TestGpt2ConvertToOnnx::test_auto_mixed_precision
FAILED test_gpt2_to_onnx.py::TestGpt2ConvertToOnnx::test_stage1 -
TypeError: ...
FAILED test_gpt2_to_onnx.py::TestGpt2ConvertToOnnx::test_stage2 -
TypeError: ...

For failure below, SkipLayerNormal is fused:
FAILED
test_optimizer.py::TestModelOptimization::test_huggingface_openaigpt_fusion