use PEP 589 syntax for TypeDict

[holmanb]

Use PEP 589 syntax for TypeDict annotation.

Also fixes previously broken typing MetaSchema typing implementation.

[TheRealFalcon]

The old version had

if sys.version_info >= (3, 8) and hasattr(typing, "TypeDict"):

That's TypeDict rather than TypedDict, so this never actually worked.

In order for this proposed version to work, we also need to add this type to every meta definition because apparently you can't coerce a raw dict into a TypedDict. E.g., on cc_apk_configure, I currently see:

Can we update these meta definitions in this PR too?

[TheRealFalcon]

This needs to inherit from TypedDict.

[holmanb]

@TheRealFalcon I rebased on the new mypy commit and it looks like the fix you suggested allows us to remove a couple of files from the "exclude" list. This is ready for re-review.

[TheRealFalcon]

Nice! LGTM.