InferTypesTransformer ignores tuples
There is no `visit_Tuple` in `InferTypesTransformer`.

It needs to be roughly the same as the `visit_List`, except replacing `List` in the return value with `Tuple`.

That is the easy part; creating test cases is the hard part, because of various problems in the transpilers related to tuples.

There are several issues like https://github.com/adsharma/py2many/issues/372 related to tuples with mixed types. e.g. a different set of bugs occur when doing `x = (1, "foo")`.

Note that any annotations are lost when destructing if we only use Python 3 annotations.  We may be able to use Python 2 annotation comments.

```py
    (b3: int, b4: str) = (1, "foo")
       ^
SyntaxError: invalid syntax
```