benchmarks: add and fix some benchmarks

[copybara-service]

benchmarks: add and fix some benchmarks

benchmarks: add and fix some benchmarks

1. add syscallbench benchmark for syscall performance
2. add hackbench benchmark for scheduler performance
3. add more threads arguments for sysbench benchmark
4. fix wrong file size for fio read
5. add more blocksize arguments for fio benchmark
6. fix invalid option of length for iperf benchmark
7. add length and parallel options for iperf benchmark

FUTURE_COPYBARA_INTEGRATE_REVIEW=#7989 from cedriccchen:benchmarks bef569a