[BUG]: AWS RDS Data API throws error on `db.$count`

### Report hasn't been filed before.

- [x] I have verified that the bug I'm about to report hasn't been filed before.

### What version of `drizzle-orm` are you using?

0.39.3

### What version of `drizzle-kit` are you using?

0.30.4

### Other packages

_No response_

### Describe the Bug

Calling `db.$count(...)` with a `drizzle` client from `drizzle-orm/aws-data-api/pg` and the `RDSClient` from `RDSDataClient` results in the following error:
```
TypeError: Cannot read properties of undefined (reading 'count')
at _AwsDataApiSession.count (/var/task/index.js:327929:13)
```

Replacing it with `db.select({ count: count() }).from(...)` works totally fine. I assume the [`AwsDataApiSession` class](https://github.com/drizzle-team/drizzle-orm/blob/main/drizzle-orm/src/aws-data-api/pg/session.ts#L153) just needs its own implementation of `count()`.