[C++][Benchmark] Benchmarks should present a items/s or bytes/s metric

[pitrou]

Describe the enhancement requested

Some of our microbenchmarks only present an iteration time in (nano,micro...)seconds. That is usually tedious to read and difficult to interpret. We should try to ensure that benchmarks also present a items/seconds and/or a bytes/seconds metric where that makes sense.

Component(s)

Benchmarking, C++

Subtasks

• [x] #39663
• [x] #39664
• [x] #39665
• [x] #39666
• [x] #39667
• [x] #39668
• [x] #39669

[pitrou]

I'm going to close this as all done.