feat(benches): set number of bytes in all benches
feat(benches): set number of bytes in all benches

This makes the benchmark runner print the throughput like this:

    test bench_httparse ... bench:         445 ns/iter (+/- 18) = 1579 MB/s
    test bench_pico     ... bench:         341 ns/iter (+/- 14) = 2061 MB/s

seanmonstar/httparse,chills42/icaparse