Summary

If a symbol x has type Any, x.__class__ should still be a dynamic, unknown type. However, that doesn't mean that it has to be Any exactly. We know that for any object x, x.__class__ will be an instance of type; if x has type Any, this still holds true, we just don't know which exact instance of type we have for x.__class__. This can be expressed using the type type[Any].

To implement these semantics, this PR modifies Type::to_meta_type so that the meta-type of Any is type[Any], the meta-type of Unknown is type[Unknown] and the meta-type of Todo is type[Todo].

Test Plan

New mdtests added