Deprecate Java 8 and support module

[Ao-senXiong]

Places we need to look for Annotatedfor to support module:

Suppress warnings:

checker-framework/framework/src/main/java/org/checkerframework/framework/source/SourceChecker.java

Line 2274 in c3e8971

public boolean shouldSuppressWarnings(@Nullable TreePath path, String errKey) {

Applying defaulting:

checker-framework/framework/src/main/java/org/checkerframework/framework/util/defaults/QualifierDefaults.java

Line 663 in c3e8971

if (!elementAnnotatedForThisChecker) {

There comment seems wrong for applying default as getEnclosingElement() will return module if module-info exisit. See If this is a package, its module is returned if such a module exists. Otherwise, null is returned

However, we still need to decide the TODO should AnnotatedFor apply to subpackages??. Looks like the logic should be more consistent if we want to handle module correctly.

          We should also start thinking about proper handling for modules. We should similarly look whether there is an annotation on an enclosing module. To do this, it would be easiest to assume we run on Java 9+. So maybe it is time to drop Java 8 support and have Java 11 as minimum requirement. Can you open an issue in which we collect all the places where modules would need to be handled?

Originally posted by @wmdietl in #1034 (comment)