Convert to the bench built-in once it is ready

[lu-zero]

Tracking issue: rust-lang/rust#29553

[lu-zero]

Related issue rust-lang/rust#50297

[djrenren]

Heads up, the most likely case is that following rust-lang/rust#50297 bench will be made an external crate that consumes those APIs (shouldn't really change the heart of this issue though)

[lu-zero]

Hopefully the change would be still minimal :)

[lu-zero]

I opened #507 as an alternative path. Criterion offers quite a number of good features out of box and seems a good fit since we plan to give a try at native SIMD now that at least some of it is available on stable rust.

[rzumer]

Closing this issue since the alternative solution was merged.