gh-106168: PyTuple_SET_ITEM() now checks the index (#106164)

PyTuple_SET_ITEM() and PyList_SET_ITEM() now check the index argument
with an assertion if Python is built in debug mode or is built with
assertions.

* list_extend() and _PyList_AppendTakeRef() now set the list size
  before calling PyList_SET_ITEM().
* PyStructSequence_GetItem() and PyStructSequence_SetItem() now check
  the index argument: must be lesser than REAL_SIZE(op).
* PyStructSequence_GET_ITEM() and PyStructSequence_SET_ITEM() are now
  aliases to PyStructSequence_GetItem() and
  PyStructSequence_SetItem().