C API: Deprecate PyImport_ImportModuleNoBlock() function

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The PyImport_ImportModuleNoBlock() function is an alias to PyImport_ImportModule() since Python 3.3. I propose to deprecate it and schedule its removal in Python 3.15.

Linked PRs

• gh-105396: Deprecate PyImport_ImportModuleNoBlock() function #105397

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The PyImport_ImportModuleNoBlock() function is an alias to PyImport_ImportModule() since Python 3.3.

It's related to this main importlib change in Python 3.3: A Finer-Grained Import Lock

Previous versions of CPython have always relied on a global import lock. This led to unexpected annoyances, such as deadlocks when importing a module would trigger code execution in a different thread as a side-effect. Clumsy workarounds were sometimes employed, such as the PyImport_ImportModuleNoBlock() C API function.

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I propose to deprecate it and schedule its removal in Python 3.15.

Since the function is part of the stable ABI, it has to stay at the ABI level, but will be removed from the C API level.