Add the ability to rerun tests that failed last

[matanlurey]

i.e. pub run test --rerun

Obviously you'd need to keep state of what failed last run, but that's probably fine?

It probably could be implemented as a separate runner using the machine readable output format and --plain-name multiple times - but there isn't actually a way to say "match this whole string, not substring" - so it won't always work.

[nex3]

Duplicate of #329.