Type and signature augmentation of the Java standard library and other libraries

[vandmo]

A bit related to #7871 but I think the question warrants being discussed on a higher level.

Python has https://github.com/python/typeshed and TypeScript has https://github.com/DefinitelyTyped/DefinitelyTyped and both have made a huge impact.

Except for explicit nulls it seems like Caprese would benefit a lot of having information about which capabilities are needed for various functions in the Java API.

[mwisnicki]

IntelliJ has external annotations that carry some of this information: https://github.com/search?q=org%3AJetBrains+path%3Aannotations.xml&type=code&p=1

CheckerFramework also has something similar.

[vandmo]

I think something like additional JAR files containing only something like tasty files but only the the type/function signatures (not sure if that is actually supported in tasty).

CheckerFramework seems like a good static analysis tool to be able to automate the creation of those files.