Incremental test output looks wonky

[pchiusano]

When using the test command, if the results aren't cached (say, because you've just done an update), you get this:

https://github.com/unisonweb/unison/assets/11074/2773700e-2a19-4e7b-b329-8df429f11bcf

I think it's trying to keep overwriting the same line rather than outputting a whole bunch of lines for each passing test, but somehow it's getting garbled.