Add support for generic NamedTuple

[erictraut]

Python 3.11 is adding runtime support for generic NamedTuple classes. Pyright should likewise support this.

python/cpython#92027

[erictraut]

This will be included in the next release.

[erictraut]

This is included in pyright 1.1.244, which I just published. It will also be included in the next release of pylance.