Migrate static Types class to TypeContext

[brandjon]

Currently, hardcoded types like list are accessed on a namespace class Types. This makes it difficult to programmatically construct types with field/method APIs, e.g. adding append() as a method of list.

We should refactor the injectable types into an interface, and have BuiltinManager implement the interface. Then we can thread that object through parts of the code that need to construct such types.