Fix `isAssignable` for `ResolvableType.forRawClass` so that it can be used with types backed by a `TypeVarible`. Prior to this commit the rawClass value was used, which wouldn't always work. Closes gh-23321
Fix `isAssignable` for `ResolvableType.forRawClass` so that it can be used with types backed by a `TypeVarible`. Prior to this commit the rawClass value was used, which wouldn't always work. Closes gh-23321