benches: fix compilation errors

[newpavlov]

Also fix benches CI job and tweak ascon-aead benchmarks to make them more consistent with other benchmarks.

Closes #549

[tarcieri]

Hmm, benches.yml should probably run whenever any of the relevant crates are changed, or we should factor it into the individual crate-related .yml files and only run focused benchmarks for the one(s) that is/are changed.

It seems like because we don't have something like that, these breakages weren't spotted along with the breaking changes.

[newpavlov]

I agree that we should run it on changes in the relevant crates, but it's not the reason why the breakage was not caught. It was because cargo build --release does not build benches.