refactor input_output_no_UU.t

Does Devel::Hide's job manually.  Drops all tests and
invokes input_output.t instead to keep these tests in sync.
stop using Test::Deep (is_deeply from Test::More is perfectly sufficient)
call SUPER::DOES from DOES
add Toby Inkster to mailmap file
Remove test dependencies

Makes Test::FailWarnings optional and uses a hand-rolled
implementation like Test::Fatal
remove File::pushd as test dependency
tidy TestUtils
add [OnlyCorePrereqs] to dist.ini
update Changes and meta