Test rule for muting System.out/err and j.u.logging in tests

(until failure happens, where stuff that the test printed actually gets printed)

Very useful in e.g. server tests which are very chatty to console. Many
tests are now muted with this rule.

There are still 10 lines or so being printed, but it might break my back
to hunt for them. Given the time spent it's a pretty good coverage of mutage.