FirstClassCallableRector should also change simple function names

# Feature Request

Currently, `FirstClassCallableRector` will transform this code:

```diff
-$result = array_map([$this, 'removeWhitespace'], $input);
+$result = array_map($this->removeWhitespace(...), $input);
```

It would be great if it could also transform this:

```diff
-$result = array_map('trim', $input);
+$result = array_map(trim(...), $input);
```

 