[ONNX] Update legacy code, initialize onnx_shape_inference=True by default (#82767)
Legacy code has onnx_shape_inference=False by default, which is misleading
as every other export api sets it to True unless otherwise overriden by caller.
There is only two tests that need updating according to this change.
* test_utility_funs.py::test_constant_fold_shape. The resulting number of nodes
in graph is increased by 1, due to that previously the extra constant node was
added as initializer.
* test_utility_funs.py::test_onnx_function_substitution_pass. Enabling onnx
shape inference discovered discrepancy in test input shape and supplied dynamic
axes arguments.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/82767
Approved by: https://github.com/justinchuby, https://github.com/abock
