Allow StrEnum members to be used as keys in TypedDict

[olejorgenb]

Cross posted to https://discuss.python.org/t/allow-strenum-members-to-be-used-as-keys-in-typeddict/64509 since that's a more active discussion fora(?)

Making TypedDict work with keys of other types like StrEnum would require a change to the TypedDict specification [this pyright comment]

from enum import StrEnum
from typing import Final, TypedDict

A = 'a'

class Foo(StrEnum):
    a = 'a'

class Bar(TypedDict):
    a: int

bar: Bar = {A: 1}  # Ok
bar2: Bar = {Foo.a: 1}  # Error: Expression of type "dict[Foo, int]" cannot be assigned to declared type "Bar"
bar3: Final[Bar] = {Foo.a: 1}  # As above
bar[Foo.a]  # Error: Could not access item in TypedDict;  "Literal[Foo.a]" is not a string literal