ci: enable report benchmark diff on a PR basis

[v1v]

Notify go benchmark report on a GitHub comment

similar to elastic/apm-server#8471

See #124 (comment)

[elasticmachine]

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• Start Time: 2022-08-31T13:48:51.407+0000

• Duration: 3 min 0 sec

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Test	Results
Failed	0
Passed	397
Skipped	40
Total	437

[elasticmachine]

📚 Go benchmark report

Diff with the main branch

name                                  old time/op    new time/op    delta
pkg:github.com/elastic/go-libaudit/v2/aucoalesce goos:linux goarch:amd64
pkg:github.com/elastic/go-libaudit/v2/auparse goos:linux goarch:amd64
ExtractKeyValuePairs/short_message-8    2.33µs ± 2%    2.44µs ± 4%  +4.65%  (p=0.016 n=5+5)

name                                  old alloc/op   new alloc/op   delta
pkg:github.com/elastic/go-libaudit/v2/aucoalesce goos:linux goarch:amd64
pkg:github.com/elastic/go-libaudit/v2/auparse goos:linux goarch:amd64

name                                  old allocs/op  new allocs/op  delta
pkg:github.com/elastic/go-libaudit/v2/aucoalesce goos:linux goarch:amd64
pkg:github.com/elastic/go-libaudit/v2/auparse goos:linux goarch:amd64

report generated with https://pkg.go.dev/golang.org/x/perf/cmd/benchstat

[cachedout]

Seems fine to enable but the output doesn't seem very useful at present. Perhaps in the future additional benchmarks will be added?

[v1v]

Seems fine to enable but the output doesn't seem very useful at present. Perhaps in the future additional benchmarks will be added?

Maybe, I don't know much about this project.

Short story, I added this particular automation as I saw #116 (review) and realise they could benefit from those benchmarks if they were running on the CI, since it was already done for some other Golang projects, it was easy to enable it :)

Additionally, this PR helps to ship the benchmark to the Cloud Benchmark Cluster, similarly done for other microbenchamrking in the APM Agents. Teams can then create their own visualisation in Kibana and reporting.