Handling of anonymous classes in CFG visualization

Take the following simple example:

class Anon {
  void foo() {
    Object o = new Object() { public String toString() { return "Special"; } };
  }
}

The anonymous object creation is displayed like a normal object creation:
new Object() [ ObjectCreation ] > @Initialized @NonNull <anonymous Anon$1>
(At least the type makes it clear that it is an anonymous object.)

org.checkerframework.dataflow.cfg.CFGBuilder.CFGTranslationPhaseOne.visitNewClass(NewClassTree, Void) should use a more appropriate name.

For the above example, the following dot files are generated when running javac -processor nullness Anon.java -Aflowdotdir=dot:

Anon-foo-KeyForSub.dot
Anon-foo-Nullness.dot
Anon-_init-KeyForSub.dot
Anon-_init-Nullness.dot
-_init-KeyForSub.dot
-_init-Nullness.dot
methods.txt
-toString-KeyForSub.dot
-toString-Nullness.dot

Note how the name for the anonymous class is missing, which makes the result hard to read, in particular if there are multiple anonymous classes, and command-line handling difficult.

Start at org.checkerframework.dataflow.cfg.CFGBuilder.CFGTranslationPhaseOne.visitNewClass(NewClassTree, Void) and reproduce the example with javac -processor nullness Anon.java -Aflowdotdir=dot. Inspect the generated dot filenames and methods.txt, then make the anonymous class name appear consistently so multiple anonymous classes remain distinguishable and command-line handling is not hindered.