benches: Add dot product benchmarks for zip meethods
benches: Add dot product benchmarks for zip meethods

The dot product shows if the zip loop is transparent enough to the optimizer
that it can be vectorized. Unfortunately, the regular .zip() loop can't!

ZipSlices and ZipTrusted both work fine.

The mystery is that i32 vectorizes and f32 doesn't..

rust-itertools/itertools,tempbottle/rust-itertools,imp/rust-itertools,flo-l/rust-itertools