Update cmd/doc and go/doc for the generics, by adding handling for type
parameters and the new embedded interface elements.
- Format type parameters when summarizing type and function nodes.
- Find the origin type name for instantiation expressions, so that
methods are associated with generic type declarations.
- Generalize the handling of embedding 'error' in interfaces to
arbitrary predeclared types.
- Keep embedded type literals.
- Update filtering to descend into embedded type literals.
Also add "any" to the list of predeclared types.
Trust: Robert Findley <email@example.com>
Run-TryBot: Robert Findley <firstname.lastname@example.org>
TryBot-Result: Go Bot <email@example.com>
Reviewed-by: Robert Griesemer <firstname.lastname@example.org>
Closing this release blocker, since we should now support generic code in go/doc and cmd/doc. But historically go/doc changes have been subtle. @jba will be updating pkgsite, which contains a fork, and may file additional issues as needed.