Remove private _PyCodec_Lookup() function

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Remove the following private functions of the C API:

• _PyCodecInfo_GetIncrementalDecoder()
• _PyCodecInfo_GetIncrementalEncoder()
• _PyCodec_DecodeText()
• _PyCodec_EncodeText()
• _PyCodec_Forget()
• _PyCodec_Lookup()
• _PyCodec_LookupTextEncoding()

Move these functions to a new pycore_codecs.h internal header file.

These functions are no longer exported.

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Code search on PyPI top 5,000 projects: only 2 projects mention these functions. In fact, orjson only mentions them in comments, and pyodbc only calls _PyCodec_Lookup() in a code which is only built on Python 2: use PyCodec_KnownEncoding() on Python 3.

PYPI-2023-04-13/orjson-3.8.10.tar.gz: orjson-3.8.10/local_dependencies/pyo3-ffi/src/codecs.rs: // skipped non-limited _PyCodec_Lookup from Include/codecs.h
PYPI-2023-04-13/orjson-3.8.10.tar.gz: orjson-3.8.10/local_dependencies/pyo3-ffi/src/codecs.rs: // skipped non-limited _PyCodec_Forget from Include/codecs.h
PYPI-2023-04-13/orjson-3.8.10.tar.gz: orjson-3.8.10/local_dependencies/pyo3-ffi/src/codecs.rs: // skipped non-limited _PyCodec_LookupTextEncoding from Include/codecs.h
PYPI-2023-04-13/orjson-3.8.10.tar.gz: orjson-3.8.10/local_dependencies/pyo3-ffi/src/codecs.rs: // skipped non-limited _PyCodec_EncodeText from Include/codecs.h
PYPI-2023-04-13/orjson-3.8.10.tar.gz: orjson-3.8.10/local_dependencies/pyo3-ffi/src/codecs.rs: // skipped non-limited _PyCodec_DecodeText from Include/codecs.h
PYPI-2023-04-13/orjson-3.8.10.tar.gz: orjson-3.8.10/local_dependencies/pyo3-ffi/src/codecs.rs: // skipped non-limited _PyCodecInfo_GetIncrementalDecoder from Include/codecs.h
PYPI-2023-04-13/orjson-3.8.10.tar.gz: orjson-3.8.10/local_dependencies/pyo3-ffi/src/codecs.rs: // skipped non-limited _PyCodecInfo_GetIncrementalEncoder from Include/codecs.h
PYPI-2023-04-13/orjson-3.8.10.tar.gz: orjson-3.8.10/include/pyo3/pyo3-ffi/src/codecs.rs: // skipped non-limited _PyCodec_Lookup from Include/codecs.h
PYPI-2023-04-13/orjson-3.8.10.tar.gz: orjson-3.8.10/include/pyo3/pyo3-ffi/src/codecs.rs: // skipped non-limited _PyCodec_Forget from Include/codecs.h
PYPI-2023-04-13/orjson-3.8.10.tar.gz: orjson-3.8.10/include/pyo3/pyo3-ffi/src/codecs.rs: // skipped non-limited _PyCodec_LookupTextEncoding from Include/codecs.h
PYPI-2023-04-13/orjson-3.8.10.tar.gz: orjson-3.8.10/include/pyo3/pyo3-ffi/src/codecs.rs: // skipped non-limited _PyCodec_EncodeText from Include/codecs.h
PYPI-2023-04-13/orjson-3.8.10.tar.gz: orjson-3.8.10/include/pyo3/pyo3-ffi/src/codecs.rs: // skipped non-limited _PyCodec_DecodeText from Include/codecs.h
PYPI-2023-04-13/orjson-3.8.10.tar.gz: orjson-3.8.10/include/pyo3/pyo3-ffi/src/codecs.rs: // skipped non-limited _PyCodecInfo_GetIncrementalDecoder from Include/codecs.h
PYPI-2023-04-13/orjson-3.8.10.tar.gz: orjson-3.8.10/include/pyo3/pyo3-ffi/src/codecs.rs: // skipped non-limited _PyCodecInfo_GetIncrementalEncoder from Include/codecs.h

PYPI-2023-04-13/pyodbc-4.0.38.tar.gz: pyodbc-4.0.38/src/pyodbccompat.cpp: PyObject* codec = _PyCodec_Lookup(encoding);

pyodbc compatibility function:

#if PY_MAJOR_VERSION < 3
int PyCodec_KnownEncoding(const char *encoding)
{
    PyObject* codec = _PyCodec_Lookup(encoding);

    if (codec)
    {
        Py_DECREF(codec);
        return 1;
    }

    PyErr_Clear();
    return 0;
}
#endif