Fix annotation default values extraction

[dreab8]

in case of

public @interface JoinTable {
   ....
    ForeignKey inverseForeignKey() default @ForeignKey(ConstraintMode.PROVIDER_DEFAULT);
  ...
}

the value returned by getAttributeMethod().getDefaultValue() is an instance of Annotation, so we need to convert it in a DynaicAnnotationUsage.

When the default value is a multi value

JoinColumn[] joinColumns() default {};

the value returned by getAttributeMethod().getDefaultValue() is an array but we later try to acces it as a list,
List<E> AttributeUsage#getList(String name);

[dreab8]

it seems Arrays.asList( defaultValue ) is not the correct way to convert array default values to a list, it causes an UnsupportException when trying to add a new element to the list.

[mbellade]

LGTM, just left a couple comments!

[sebersole]

Overall looks good.