This does two changes that are quite related.

0. it add that variable binding can occur in pattern matching, an update of 3.10
which seems to have been omitted from the list of bindings
1. Given how long the sentence already was, with even subcases in the middle of
the sentence, the commit breaks the sentence into an actual list.

A similar sentence is present in the 'Invocation from super' section of
the descriptor HOWTO, where it is already correct.

It is now considered a historical accident that e.g. `for` loops and the `iter()` built-in function do not require the iterators they work with to define `__iter__`, only `__next__`.

Co-authored-by: Łukasz Langa <lukasz@langa.pl>

The documentation explaining Python's data model does not adequately explain
the differences between ``__getitem__`` and ``__class_getitem__``, nor does it
explain when each is called. There is an attempt at explaining
``__class_getitem__`` in the documentation for ``GenericAlias`` objects, but
this does not give sufficient clarity into how the method works. Moreover, it
is the wrong place for that information to be found; the explanation of
``__class_getitem__`` should be in the documentation explaining the data model.

This PR has been split off from GH-29335.

It should be noted that this part of the documentation is redundant with
function.rst's documentation of int. This one was correctly updated with Python 3.8.

Keep track of whether unsafe_tuple_compare() calls are resolved by the very
first tuple elements, and adjust strategy accordingly. This can significantly
cut the number of calls made to the full-blown PyObject_RichCompareBool(),
and especially when duplicates are rare.

Co-authored-by: Łukasz Langa <lukasz@langa.pl>