Report max RSS as part of compare_benchmarks

[mrks]

In #2294, I almost introduced significant memory costs. I wonder if we should store the Max RSS (getrusage / ru_maxrss, no idea about Mac) in the benchmark JSON and make that part of the compare_benchmark output. If yes, we should make sure that it is visible for benchmark_all even without unfolding the system comparison part.

[mrks]

We can probably reuse code from MetaSystemUtilizationTable or add MaxRSS over there and simply drag it into the output JSON.