Farmer audit benchmark

[nazar-pc]

This adds auditing benchmark to the farmer, which can be used with existing plot. We will use this going forward to ensure changes we do to the auditing are actually improvements as well as to compare different potential implementations.

The usage is very simple:

subspace-farmer benchmark audit /media/nazar-pc/subspace-farm

The output will look like this:

Benchmarking audit/plot
Benchmarking audit/plot: Warming up for 3.0000 s
Benchmarking audit/plot: Collecting 10 samples in estimated 6.2718 s (220 iterations)
Benchmarking audit/plot: Analyzing
audit/plot              time:   [28.478 ms 28.586 ms 28.697 ms]
                        thrpt:  [ 24216 GiB/s  24310 GiB/s  24402 GiB/s]

It prints both full audit time and throughput that takes plot size into account. In example above auditing speed is ~24TiB/s.

First few commits are just refactoring, the benchmark implementation is one commit at the end.

Resolves #1914

Code contributor checklist:

• I have read, understood and followed contributing guide

[nazar-pc]

Windows is so annoying...

[shamil-gadelshin]

A tiny change request. Makes sense otherwise.

[jim-counter]

LGTM!

[EmilFattakhov]

Thanks Nazar, noted!