WIP: Look for changed significantly metrics and notify authors

[punchagan]

This PR looks for PRs where metrics have changed significantly and attempts to post messages to the corresponding Github PR to notify authors to check the metrics.

[punchagan]

A sample bot message/comment would look like this:

---

#2 (40a7f39) changes the metrics as follows in comparison to main (b5a7c3b) when running on autumn (ocaml/opam:debian-11-ocaml-4.13):

Benchmark: default

Test: bench_1_test_1

• grammarFunctor/generate changed by 42.857143%
• grammarFunctor/parsing changed by 5.263158%
• grammarFunctor/typing changed by -28.571429%
• mbs_per_sec changed by -4.522613%
• ops_per_sec changed by -1.449275%

Test: bench_1_test_2

• mbs_per_sec changed by -41.176471%
• ops_per_sec changed by 2.061856%
• time changed by -9.057971%
• yo is a new metric

[art-w]

So cool! Would it be possible to add a setting per repository to opt-in this feature? (I would like to test it in production on safe repositories before enabling it for everyone ^^' )

[punchagan]

Would it be possible to add a setting per repository to opt-in this feature?

I've added a config option that can be added to development.conf or production.conf to opt-in for Github notifications, per repository.

[punchagan]

I see some new empty boxes added in the graph, and with an initial look at the API, I wasn't sure how to hide or label them. Could you help with that, @art-w ? :see_no_evil:

[art-w]

I think the empty-boxes are due to the various let* that we should eventually get rid of (but weren't introduced by your nice PR!)

https://github.com/ocurrent/current-bench/blob/37ad8acc485f6fe70ebd0a56d3c91b2679b1d5d9/pipeline/lib/pipeline.ml#L147

[art-w]

Thanks a lot for all the changes!