* NET-2397: Add readme.md to upgrade test subdirectory
* remove test code
* fix link and update steps of adding new test cases (#16654)
* fix link and update steps of adding new test cases
* Apply suggestions from code review
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Co-authored-by: cskh <hui.kang@hashicorp.com>
Co-authored-by: Nick Irvine <115657443+nfi-hashicorp@users.noreply.github.com>