JAIF-based whole program inference known issues

Discovered while testing stub-backed WPI (#2871).

The failing test is ConflictingAnnotationsTest.java, which will be merged with #2871 but disabled for jaif-based WPI:

// Tests whether inferring an @Sibling1 annotation when another
// @Sibling1 annotation from a different namespace is present causes
// problems.

class ConflictingAnnotationsTest {

    int getWPINamespaceSibling1() {
        return MethodReturnTest.getSibling1();
    }

    // This version of Sibling1 is not typechecked - it doesn't
    // belong to the checker and instead is defined in the Sibling1.java
    // file in this directory.
    @Sibling1 int getLocalSibling1() {
        return 1;
    }
}

There is also the definition of the alternative @Sibling1 annotation in the WPI test directory.

JAIF-based WPI blindly imports testlib.wholeprograminference.qual.Sibling1 annotation, causing a conflicting annotations error to be issued on the return type of the getLocalSibling1 method (which also has WholeProgramInferenceBottom inferred.

The workaround to prevent the jaif-based version from running on this test is to delete the test from the annotated subdirectory before checking for errors after WPI runs.

Start with ConflictingAnnotationsTest.java and the alternative Sibling1.java in the WPI test directory, then compare the JAIF-based WPI handling described for #2871. Reproduce the conflicting-annotation error and inspect the annotated subdirectory workaround; done means the test no longer receives the incorrect imported annotation without relying on deleting it.