Add ability to visit an entire library

[JoshLove-msft]

We have the ability to visit types and their members, but there are scenarios where it is useful to change something about type Foo based on type Bar. Currently, there isn't a good way to do this as the ordering of when types will be visited is not defined or configurable. We don't want customers to take a dependency on order. We should introduce a method that visits the OutputLibrary.