[issue35266] Add _PyPreConfig and rework _PyCoreConfig and _PyMainInterpreterConfig

[STINNER Victor]

Change by STINNER Victor <vstinner at redhat.com>:


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keywords: +patch
pull_requests: +9823
stage:  -> patch review

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue35266>
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