test: add broken roundtrip test

test: add broken roundtrip test

We demonstrate the current notmuch restore parser being confused by
message-id's and tags containing non alpha numeric characters
(particularly space and parentheses are problematic because they are
not escaped by notmuch dump).

We save the files as hex escaped on disk so that terminal emulators
will not get confused if the test fails (as we mostly expect it to do).