Update Custom C++ and CUDA Operators to use PyTorch stable API/ABI

[mikaylagawarecki]

Description

Migrate advanced_source/cpp_custom_ops.rst to libtorch stable ABI/API. Accompanying change to extension-cpp

Checklist

• [ ] The issue that is being fixed is referred in the description (see above "Fixes #ISSUE_NUMBER")
• [ ] Only one issue is addressed in this pull request
• [ ] Labels from the issue that this PR is fixing are added to this pull request
• [ ] No unnecessary issues are included into this pull request.

cc @zou3519