Make sure core schema types are unique

### Initial Checks

- [X] I confirm that I'm using Pydantic V2

### Description

- e.g. https://github.com/pydantic/pydantic/pull/11085#discussion_r1878866065 (function schemas)
- enforce the uniqueness

### Example Code

_No response_

### Python, Pydantic & OS Version

```Text
2.10
```
