Show summary line for tests run and passed

[petemounce]

... so that it's possible to see that "the normal number of" tests ran and passed. Sometimes someone might delete a swathe of tests or change build-automation in a way that causes them to no longer run (by mistake); the summary line would allow that to be noticed slightly easier (though I recognise it's definitely not a guarantee). Ideally inside a success or info annotation?

[maschwenk]

We currently don’t have our own use case for this, but PRs are welcome as it sounds like it could be useful to others