Remove unused `ElementType`s in `@Target`

[theron-wang]

Removes unused ElementTypes in @Target annotations. The current approach is to only remove ElementTypes, not add them, so we don't accidentally make a non TYPE_USE annotation into a TYPE_USE annotation, for example.

I also addressed two small bugs I encountered:

• When all the wildcard import are JDK imports, synthetic classes should be generated in the current package instead of the first wildcard import package
• Don't throw an exception when an annotation is applied on a package declaration

Instead of creating a new test case for this, I just modified one of the existing ones (SyntheticAnnotationTargetTest), since it's purpose already seemed to fit this PR.

Thanks!

[kelloggm]

@theron-wang can you resolve the merge conflict? It should be easy: you just need to decide whether the code in this PR or the code in #354 (which I just merged) should run first.