Add support for @CheckReturnValue

IntelliJ has a "clever" way to inform the users that the result of a method must be used.
It detects that the method is annotated with a @CheckReturnValue annotation regardless of its package. So, frameworks can provide their own (like SmallRye Commons Annotations).

Basically, if you have an API with:

@CheckReturnValue
public Uni<String> doSomethingCool();

a user using that method like in the following snippet would get a warning:

doSomethingCool();

The warning indicates that the return value must be used, like in:

doSomethingCool().subscribe().with(r -> ...);

This is particularly interesting for reactive APIs, stream APIs, and builders APIs.

It would be great if VS Code Java could provide the same kind of feature.

CC @maxandersen

未指定源文件或测试。首先定位 VS Code Java 诊断或分析的入口点，并检查方法注解的处理方式；当与包无关的 @CheckReturnValue 注解能够针对被忽略的结果产生警告，并覆盖 reactive、stream 或 builder-style 调用时，工作即完成。