improve benchmarks

[tfaoliveira-sb]

• check cpucycles
• strip benchmarking code down to the bare minimum
• add options to the main: support an option for tagging csv files (to simplify comparisons such as ssbd vs plain vs zeroization with option1 vs with option2);
• add an external folder with external implementations, bind them to the building infrastructure, and test them/bench them (to produce comparison reports -- likely README.md files)
• add script that digests benchmarking info into tables (there are already some in the formosa artifacts lying around).