ruff

6ab32a77 - [red-knot] Create generic context for generic classes lazily (#17617)

[red-knot] Create generic context for generic classes lazily (#17617) As discussed today, this is needed to handle legacy generic classes without having to infer the types of the class's explicit bases eagerly at class construction time. Pulling this out into a separate PR so there's a smaller diff to review. This also makes our representation of generic classes and functions more consistent — before, we had separate Rust types and enum variants for generic/non-generic classes, but a single type for generic functions. Now we each a single (respective) type for each. There were very few places we were differentiation between generic and non-generic _class literals_, and these are handled now by calling the (salsa cached) `generic_context` _accessor function_. Note that _`ClassType`_ is still an enum with distinct variants for non-generic classes and specialized generic classes.