Optional bounds for full count

If I want to get the full count, I'd like to just do:

```ts
aggregate.count(ctx);
// instead of
aggregate.count(ctx, {bounds: {}});
```

And for a namespace I'd like to do:
```ts
aggregate.count(ctx, { namespace: userId });
```

setting `bounds` to `{}` is not super discoverable, I assumed I needed to specify `prefix` or something.