[issue35134] Add a new Include/cpython/ subdirectory for the "CPython API" with implementation details

[hai shi]

Change by hai shi <shihai1991 at 126.com>:


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nosy: +shihai1991
nosy_count: 8.0 -> 9.0
pull_requests: +23686
pull_request: https://github.com/python/cpython/pull/24922

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue35134>
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