Update Custom C++ and CUDA Operators to use PyTorch stable API/ABI (#3701)

## Description
Migrate `advanced_source/cpp_custom_ops.rst` to libtorch stable ABI/API.
Accompanying change to
[`extension-cpp`](pytorch/extension-cpp#126)

cc @zou3519

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Co-authored-by: Alanna Burke <burkealanna@meta.com>
Co-authored-by: Svetlana Karslioglu <svekars@meta.com>

Author: 3 people