[ONNX] Add script/trace different flatten and move optional type tests to runtime (#83184)
fix #78119
Why:
As in onnx tests verification code, we used to only consider tracing output, which ignores None type, this PR enables runtime test to keep None type in torch in script mode.
1. Move Optional Type tests from no runtime to runtime, as it's supported by ONNXRUNTIME.
2. Add ignoreNone flag for output comparison of internal tests
Pull Request resolved: https://github.com/pytorch/pytorch/pull/83184
Approved by: https://github.com/justinchuby, https://github.com/BowenBao
