Undfudge and expand `is default(Mu)` test
Undfudge and expand `is default(Mu)` test

RT#132082: https://rt.perl.org/Ticket/Display.html?id=132082
Rakudo fix: https://github.com/rakudo/rakudo/commit/54507ac94e

dogbert17/roast,bitrauser/roast,bitrauser/roast,perl6/roast,dogbert17/roast