[Feature Request]: bf16 and its vector friends

### Is there an existing issue for the same feature request?

- [X] I have checked the existing issues.

### Is your feature request related to a problem?

```Markdown
Implement bf16 and its corresponding vector, sparse vector etc types.

https://en.wikipedia.org/wiki/Bfloat16_floating-point_format

Note that bf16 is NOT the same as IEEE half precision format. bf16 is a simple shortening of float32. It is much more widely used in AI world than half precision.
```

### Describe the feature you'd like

New data type.

### Describe implementation you've considered

_No response_

### Documentation, Adoption, Use Case, Migration Strategy

_No response_

### Additional information

_No response_