Expand incompleteTypes property fixes to extended generics

Following #178, let's add this:

```diff
class Component {
state: TState;
}

+ type ClickableState = {
+ clicks: number,
+ };

- class Clickable extends Component {
+ class Clickable extends Component {
state = {
clicks: 0,
};
}
```

Additionally:

```diff
- class Clickable extends Component {
+ class Clickable extends Component {
resetState() {
this.state = {
clicks: 0,
};
}
}
```