add SAVE_TEST_GRAPH macro (#18696)
### Description
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Add a macro `SAVE_TEST_GRAPH ` in `graph_transform_test_builder.cc`.
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
This will help us debug the graph and Unitest.
Co-authored-by: ruiren <ruiren@microsoft.com>
