Upstreaming: formatting of type variables

[wmdietl]

Changes from

• 5fc6c28
• and handling of verbose generics (didn't track down commit that removed that code, yet).

[cpovirk]

Is the "handling of verbose generics" you're referring to the fact that we output Foo<Bar?> and similar? If so, that's handled on the checker side by providing our own AnnotatedTypeFormatter.

I... don't know if 5fc6c28 is serving a purpose at this point or not. Maybe it matters in the debugger, but I kind of doubt that it even does there. If we're lucky, we don't need any upstream changes for this.