[jit] fix named tuples as attributes (#37251)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37251
This was broken by recent changes to how we serialize with type tags. We
save a name (like `Dict[str, MyNamedTuple]`) and then relied on the
mobile type parser to resolve that name back into a set of types.
This doesn't work for any NamedTypes as the mobile type parser doesn't
know how to resolve those. The unpickler allows the caller to inject a
type resolver in for this purpose, use that so that when importing in a
non-mobile environment you get the right results.
A second problem also had to be fixed: the SourceImporter type loader
would only load named types directly (e.g. `MyNamedTuple`) and choked if
it was a general type that contained a named tupe (e.g.
`List[MyNamedTuple]`). Fixed that and renamed `loadNamedType` to
`loadType` for clarity.
Test Plan: Imported from OSS
Differential Revision: D21235213
Pulled By: suo
fbshipit-source-id: 16db0f4c5e91a890d67a8687cc8ababa6b94b0f4
