get all traits of ancestor classes & ancestor traits

useful when using setters in traits
This merge/unique/values stuff could be avoided by using the output of `class_uses` as is:

```php
$traits += class_uses($class); // $traits += ['foo' => 'foo']
// ... at the end:
$traits = array_values($traits);
```

Then your `+=` would work as expected, no need to call `array_merge`, no need for repeated `array_unique` calls.