dillon1000/react

Resolve type aliases

The goal of this PR is to move towards a uniform representation for all type
declarations, whether they are named type aliases, function declarations, or
inline annotations. We now assign every non-primitive type declaration (named or
anonymous) a unique DeclarationId. In the next PR, we'll also re-map inline
annotations back to this declaration id when encountering them.

This PR is extremely gross and my intent is to refactor a bunch of things in the
HIR to allow this to be less gross. Challenges:

* Babel name resolution requires using scopes but i really want to just work
with plain nodes, since NodePath and TypeScript do _not_ get along. So here, i
find all identifiers and store a mapping of identifier -> scope, so that i can
later look them up if necessary.

* HIR doesn't have a notion of a declaration id, and in general we don't want
to extend HIR. So i end up with a whole bunch of side table information and
indirection. For example, a function doesn't know it's own declaration id.
So we have to look it up. Function params don't track their Forest type, so
we have to look them up on the function declaration. Etc.