gh-157044: Preserve asyncio call stacks through callable aiter()

[goutamadwant]

Fixes #157044.

Expose the callable iterator awaitable's wrapped object through a read-only aw_wrapped attribute and follow it when building asyncio call graphs. The wrapper contributes no frame. Release/acquire atomics protect concurrent publication and introspection.

Add regression coverage for both asyncio backends, nested callable iterators, frame limits, and the wrapped object's lifecycle. Iteration behavior is unchanged.

Validation:

• Debug-build module run: 3,738 tests run, 80 skipped.
• Focused reference-leak checks passed.
• Patchcheck passed.
• Free-threaded runtime tests were not run.

• Issue: asyncio.print_call_graph() loses the call stack at aiter(callable, stop_value) #157044

[read-the-docs-community]

Documentation build overview

📚 cpython-previews | 🛠️ Build #34464668 | 📁 Comparing ba728ed against main (1ac3bfa)

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2 files changed

± library/functions.html
± whatsnew/changelog.html