Handling `Literal` type in annotations.
Resolves: #13672
## Implementation
Since Literals are not a fully defined type in typeshed. I used a trick
to figure out when a special form is a literal.
When we are inferring assignment types I am checking if the type of that
assignment was resolved to typing.SpecialForm and the name of the target
is `Literal` if that is the case then I am re creating a new instance
type and set the known instance field to `KnownInstance:Literal`.
**Why not defining a new type?**
From this [issue](https://github.com/python/typeshed/issues/6219) I
learned that we want to resolve members to SpecialMethod class. So if we
create a new instance here we can rely on the member resolving in that
already exists.
## Tests
https://typing.readthedocs.io/en/latest/spec/literal.html#equivalence-of-two-literals
Since the type of the value inside Literal is evaluated as a
Literal(LiteralString, LiteralInt, ...) then the equality is only true
when types and value are equal.
https://typing.readthedocs.io/en/latest/spec/literal.html#legal-and-illegal-parameterizations
The illegal parameterizations are mostly implemented I'm currently
checking the slice expression and the slice type to make sure it's
valid.
https://typing.readthedocs.io/en/latest/spec/literal.html#shortening-unions-of-literals
---------
Co-authored-by: Carl Meyer <carl@astral.sh>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
