bench, doc: benchmarking updates and fixups

[jonatack]

Fixups and updates I noticed while writing benchmarks for #22284.

[kiminuo]

Concept ACK

Thanks for improving this.

[jarolrod]

Concept ACK, is obviously an improvement to the docs

[jonatack]

Thanks @fanquake, @jarolrod and @kiminuo for the reviews. Updated per feedback and fixed the last commit message (bencharking -> benchmarking).

[theStack]

Concept ACK, nice benchmark doc improvements!
Planning to verify the changes more in detail within the next days.

[theStack]

ACK d8513fe 🚤

Reviewed the documentation changes, ran ./src/bench/bench_bitcoin -filter="AddrManAdd|AddrManGetAddr|Base58CheckEncode|Base58Decode" to verify that the example output format in the last commit matches.

[za-kk]

ACK d8513fe

Reviewed documentation and it's definitely an improvement to what was already there, also ran ./src/bench/bench_bitcoin -filter="AddrManAdd|AddrManGetAddr|Base58CheckEncode|Base58Decode" and verified format matches with documentation

Note - running ./src/bench/bench_bitcoin -? causes an error in zsh as ? is considered a wildcard, instead ./src/bench/bench_bitcoin "-?" must be run. Now that we are specifying -? in the docs instead of --help could cause confusion when using zsh (which is default on macos). But I'm not sure whether the intricacies of different shells should impact the documentation 🤷