Correct AnnotatedIntersectionTypes

[smillst]

General facts about intersections in javac that should make this pull request easier to review:

1. In source code, intersections can only be written as a cast type or an upper bound of a type parameter.
   a. For cast types, the intersection type is parsed into an IntersectionTypeTree.
   b. For type variable upper bounds, the intersection type is parsed into a list of trees
2. In byte code, the Checker Framework only reads annotations on intersections for type parameter upper bounds.
3. Intersection types can also arise from capture conversion and least upper bounds.
4. The bounds of explicitly written intersections must be declared types, but intersections from LUB or capture conversion can be any kind of type.

Changes in this pull request:
Defaulting rules for the primary annotation of an intersection type:

1. One or more of the bounds have an explicit annotation: the default annotation is the first explicit annotation. (I tried making the default the glb of the (explicit or defaulted) annotations on the bounds, but I found this confusing in the case of casts. We can discuss this further.)
2. Zero bounds have an explicit annotation: the default annotation of the location is applied. (So, either explicit upper bound defaults, or for casts, the annotation of the cast expression.)

Warning:
If any explicit annotation on a bound is not the same as the primary annotation, then a warning is issued. (I was going to put this in a separate pull request, but it needs to be in this one so that the test cases are easier to understand.)

Changes to AnnotatedIntersectionType:

1. Adding a primary annotation to an intersection type causes that annotation to be copied to its bounds. This is similar to what happens when an annotation is added to a type variable.
2. New method getBounds returns a list of the bounds of the intersection type. (This used to be done via directSuperTypes method.
3. The bounds can be any AnnotatedTypeMirror if the intersection arises from capture conversion.

Fixes #868; Fixes #3349; Fixes #3362; Fixes #3659.

[mernst]

Overall, this looks good. Thanks! I have a couple clarifying questions.

[mernst]

In this example, the annotation isn't just copied to the primary annotation location, but to every bound of the intersection.

Also, it would be helpful to indicate that the primary annotation location is different than all the annotations on the bounds. The example doesn't actually show the primary annotation location. So, I find the example a bit confusing.

[mernst]

When this is called, have the primary annotations already been applied to every bound, so that each bound stands on its own without any need to refer to the primary annotations?

[smillst]

Yes. This method is only called on fully-annotated types. That means that the intersection type has a primary annotation for every qualifier hierarchy.

[smillst]

TOOD: Add comment.

[msridhar]

Does this also fix #3569? Just curious.

[mernst]

Yes, it does. Good catch. I have updated the pull request description and the linked issues.