Fix Java API ClassCastException when getting EnumSort of constant

- Add EnumSort(Context ctx, long obj) constructor to allow creating
  EnumSort from an existing native sort object
- Modify Sort.create() to detect enum sorts (all constructors have
  arity 0) and return EnumSort instead of DatatypeSort, mirroring
  Z3's own is_enum_sort implementation

Closes #7335

src/api/java/EnumSort.java

@@ -92,6 +92,11 @@ public class EnumSort<R> extends Sort
         return new FuncDecl<>(getContext(), Native.getDatatypeSortRecognizer(getContext().nCtx(), getNativeObject(), inx));
     }
 
+    EnumSort(Context ctx, long obj)
+    {
+        super(ctx, obj);
+    }
+
     EnumSort(Context ctx, Symbol name, Symbol[] enumNames)
     {
         super(ctx, Native.mkEnumerationSort(ctx.nCtx(),