[javac] fix quickfix to implement inherited abstract methods

[datho7561]

• add mapping for error id for missing abstract method implementations
• fixed an NPE that would prevent the error from being shown on anonymous classes
• fix binding logic for anonymous classes

example to try out: use the quickfix to add a stub implementation of method() to the anonymous class:

public class Parent {

  static interface IMethodable {
    void method();
  }

  public static void myMethod() {
    IMethodable methodable = new IMethodable() {
    };
    methodable.method();
  }

}

Future work: fix the diagnostic range on anonymous classes. We might need access to the AST, since we ideally want to highlight IMethodable from the constructor invocation.

[datho7561]

After the rebase, the return type in the generated method is now generated as invalid instead of void. I'll need to look further into it.

UPDATE: got it, void should be considered a primitive type.