Add fp16 type support

[jaychia]

Is your feature request related to a problem? Please describe.

Add fp16 as a Daft type

cc @conceptofmind

[conceptofmind]

Hi @jaychia,

I appreciate you opening this issue.

Not an immediate ask like #2899 since we can cast but definitely a quality-of-life feature would be additional support for bf16, fp16, and fp8 dtypes.

It looks like there is an available crate here as a potential reference for bf16 and fp16: https://github.com/starkat99/half-rs

Thank you,

Enrico