Exported types incompatible with ESM when using TypeScript@next

### Describe the bug

When importing `rxjs` in a project using TypeScript@next with the `"module": "nodenext"` ([experimental ESM support](https://www.typescriptlang.org/docs/handbook/esm-node.html)) it fails to locate the associated types. As seen in this TypeScript playground: [Playground Link](https://www.typescriptlang.org/play?target=99&moduleResolution=99&ts=4.6.0-dev.20220116#code/JYWwDg9gTgLgBAbzgeQEYGcCmUBuBDVAG0wBo4BlAV1QCtMBjeAXzgDMoIQ4ByKADxrpuAbiA).

### Expected behavior

TypeScript@next is experimental so I suppose I don't expect it to work. But the API seems fairly stable, so I am raising this issue to track the change. The `exports` spec defines an optional `types` field, which if used in rxjs resolved the issue (I have tried this with a patch locally).

### Reproduction code

```typescript
import { Observable, Subject } from 'rxjs';
```


### Reproduction URL

https://www.typescriptlang.org/play?target=99&moduleResolution=99&ts=4.6.0-dev.20220116#code/JYWwDg9gTgLgBAbzgeQEYGcCmUBuBDVAG0wBo4BlAV1QCtMBjeAXzgDMoIQ4ByKADxrpuAbiA

### Version

7.4.0

### Environment

- Node.js@16.13.2

- TypeScript@4.6.0-dev.20220204

### Additional context

Related discussion in the TypeScript repo: https://github.com/microsoft/TypeScript/issues/46452#issuecomment-1031564279

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