Return testing time separately for each tested commit

[LilithHafner]

Currently, I see Testing took 22 hours, 19 minutes, 37 seconds (or, sequentially, 38 days, 19 hours, 35 minutes, 44 seconds to evaluate 21532 packages). I'd like to see a breakdown of how much of that time was spent on each commit that was tested. Something like this would be perfect:

Sequentially, testing took 5.14 days on JuliaLang/julia@a39797a4fb5460cb96649dbd5dccadb903323761 and 19.40 days on JuliaLang/julia@0e1aa6c7ebb7e328e630ea206e01eb3f64a83d81

And I imagine PkgEval would need to return this info for Nanosoldier to be able to report it.