WIP test-bot: parallelize dependent test

[GunniBusch]

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Info: This is WIP, and currently NOT the final version. I am opening this PR so I can use the pr to do some testing and one can see the progress.

The goal of this PR is to introduce a way to make testing dependencies parallel. Important to know is that I dont think the actual testing is the pure problem but the other steps. I sampled the timings of a lot of homebrew core dependent tests and came to this conclusion:

This shows that testing is not that slow, but the stuff like installing and such is.

So my proposed solution is to leave testing as is and just try to better balance out the pretest stuff.

I will remove WIP once my approach is final.

PS:

Unlike my previous approach using sharding, this is supposed to have a lower footprint (eg also regarding code changes)

[MikeMcQuaid]

Hey @GunniBusch! I think this misunderstands the goal of "parallelising" here; we're not wanting to parallelise within a single GitHub Actions worker/job but to fan out to many different GitHub Actions workers/jobs.

Let me know if that doesn't make sense!

[GunniBusch]

Hey @GunniBusch! I think this misunderstands the goal of "parallelising" here; we're not wanting to parallelise within a single GitHub Actions worker/job but to fan out to many different GitHub Actions workers/jobs.

Let me know if that doesn't make sense!

Good to know. So like my prev one.
Will update this pr