Replace iterator/sort with iterator/quickSort?

[jussi-kalliokoski]

Should be perf-tested whether there are any cases where the native implementation of the sorting algorithm significantly outperforms the self-hosted version. If not, quickSort should be deprecated and the algorithm used in sort. That way, the performance will also be more predictable and the algorithm deterministic (the self-hosted version uses first element as pivot so it's referentially transparent).