Implement random.booleans()

Generate random boolean values.

If optional param `repetitions` not given then iterate infinitely.

```
function *booleans(repetitions?: number): Iterable<boolean>
```

Needs to be implemented:
* `random.booleans()`
* `random.booleansAsync()`
* `Stream.booleans()`
* `AsyncStream.booleans()`
