Make `ipfs get` as fast as `ipfs pin add`

### Checklist

- [X] My issue is specific & actionable.
- [X] I am not suggesting a protocol enhancement.
- [X] I have searched on the [issue tracker](https://github.com/ipfs/go-ipfs/issues?q=is%3Aissue) for my issue.

### Description

Right now, `ipfs pin add` is actually faster than `ipfs get` at fetching data since `ipfs pin add` does concurrent dag traversals and preheating. Ideally, `ipfs get` should also use this same method so that both are equally fast, it's not very intuitive that "pinning" is faster than "getting", many users probably don't know about the performance difference.