bd171fbb

By: lcnbr <im@lcnbr.ch>

Keep Criterion out of Momtrop library dependencies

Criterion is used only by the benchmark targets. Move it to dev-dependencies
so library consumers do not compile its benchmark and reporting dependency
closure. Preserve the published 0.3.0 numerical source and benchmark behavior.

Validation: 33 library tests and the million-sample triangle test pass;
cargo check --benches passes. Criterion is absent from normal/build edges
and remains available through the dev-dependency graph.