Add support for Nullable as a TYPE_USE annotation

I wanted to switch from JSR305 to Checker Framework @Nullable, but it breaks my @Nullable injection points:

1) null returned by binding at […]
 but the 1st parameter of […].<init>([…]) is not @Nullable

Apparently, this is because Guice only looks at field and parameter annotations, not TYPE_USE annotations: https://github.com/google/guice/blob/eface212cdf3eeb1579d6e033cd54fd1426d65ba/core/src/com/google/inject/spi/InjectionPoint.java#L117-L119

Note: I couldn’t use the Java 7-compatible annotations from the Checker Framework either because it’s named @NullableDecl, and Guice only looks at annotations named @Nullable.

[cpovirk]

It looks to me like 5.0.0 (though use 5.0.1 instead), released earlier this year, contains the change that lets you write @Nullable Foo foo for type-use annotations as well as for declaration annotations.

As discussed above, Guice could theoretically do more with type-use annotations, but this at least makes them not worse than declaration annotations. Possibly that’s enough to close this issue.

Anyone who migrates from declaration annotations to type-use annotations may need to move some annotations along the way:

• @Nullable Foo[] foo -> Foo @Nullable [] foo
• @Nullable Foo.Bar bar -> Foo.@Nullable Bar bar

(That’s just how type-use-annotation syntax works.)

(I don’t see mention of this in the release notes. Maybe it should be added?)

[cpovirk]

There are a lot of things that “Guice supports @Nullable type annotations” could mean, but https://github.com/google/guice/commit/1a410a8bef1ec721e16f9f16a447235f09951f05 accomplished the main one. I assume there hasn’t been a release yet, though.