Investigate AVX2 ML-DSA key generation slowdown

[jschneider-bensch]

AVX2 key generation seems to be slower when I run the benchmarks in this repository vs. the mainline repo. This is not super relevant for the embedded devices we're looking at, but it points to some mistake somewhere in the update. I essentially updated Cargo.toml files, if necessary, to match their mainline versions, and completely replaces the Rust sources with the new ones, so this is a bit puzzling.