gh-141004: Document missing iterator types in the C API (GH-141010)

Add documentation for each of the following:

- PyByteArrayIter_Type
- PyBytesIter_Type
- PyListIter_Type
- PyListRevIter_Type
- PySetIter_Type
- PyTupleIter_Type
- PyRangeIter_Type
- PyLongRangeIter_Type
- PyDictIterKey_Type
- PyDictRevIterKey_Type
- PyDictIterValue_Type
- PyDictRevIterValue_Type
- PyDictIterItem_Type
- PyDictRevIterItem_Type

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Co-authored-by: Petr Viktorin <encukou@gmail.com>