This wraps `Ident` in a new `Object` variant and modifies `Asg` so that its
nodes are of type `Object`.
This unfortunately requires runtime type checking. Whether or not that's
worth alleviating in the future depends on a lot of different things, since
it'll require my own graph implementation, and I have to focus on other
things right now. Maybe it'll be worth it in the future.
Note that this also gets rid of some doc examples that simply aren't worth
maintaining as the API evolves.
DEV-11864