improve log structure

[brownsarahm]

• add an identifier shared across all data generated from a version of the benchmark (e.g. make a commit whenever run is called if there are uncommitted changes to the benchmark and include the commit hash in the log file, so that users can recover the exact version of the benchmark that generated the logs)
• reduce redundancy between json, text and run_info.yml
• prepare for adding a number of repetitions to run, but still know which were run a the same batch

note goal is to simplify and make more flexible benchmark level scoring