Ref T1191. After utf8mb4 conversion, these tests no longer pass because MySQL allows emoji and gclefs and such.
We could keep these tests running by keeping a ut8f_bin table around somewhere, but we have no other use cases for it and it does not seem worth the added complexity. All these BMP-only codepaths are on the way out.
Update the %s / %B test to make sure it's rejecting invalid byte sequences, which are still not permitted.