No-op Configuration

When using flamegraph profiling rayon pollutes the call stack making it very hard to find my code in the graph, and I have to manually replace all instances of par_. It'd be nice if I could instead enable a feature flag in rayon so that I don't have to change every code instance and just have to change Cargo.toml that simply made all parallel iterator calls sequential. I've included two graphs below with and without rayon calls to show the disparity between the two.

With rayon

Without rayon