Benchmarks: shows results per single operation instead of batching operations

[roji]

Many of our benchmarks (e.g. FuncletizationTests) perform a look inside the method to avoid having the method call overhead skew the results. This is good practice, but results are reported for the batch instead of per-operation; BenchmarkDotNet allows a benchmark to expose how many operations are invoked in the function for display purposes (OperationsPerInvoke).

Requires a database cleanup as well at the same time, can do this on my next visit to Redmond.

/cc @sebastienros

[smitpatel]

Does #20821 fix this? If yes, can we put blocked label on this?