Cache types.GenericAlias in getitems

The "old-style" generic classes from the typing module (List, Dict, etc) cached typing._GenericAlias instances retuned from __getitem__:

>>> from typing import List
>>> List[int] is List[int]
True

But when this functionality was ported to built-in types, caching was not implemented:

>>> list[int] is list[int]
False

Since it is very common to subscript the same types with the same arguments, caching will be very beneficial here and will reduce memory footprint of heavily type-annotated modules.

Linked PRs

• gh-103541

Inizia esaminando il comportamento di caching esistente del modulo typing per getitem e la PR collegata gh-103541. Conferma il risultato desiderato con l'esempio list[int] is list[int]; il lavoro è completato quando gli alias generici integrati equivalenti vengono messi in cache senza modificare il comportamento dichiarato di typing.