Actually, to avoid making a breaking change, I'm deprecating
BadMessage and creating a new InvalidMessage variant that takes a
Cow. This way I don't need to track every crate that re-exposes
tor_bytes::Error and call this a breaking change in those.
Making this change will allow tor_bytes errors to be much more
helpful.
Some of these were for decoding particular objects (we now say
what kind of objects), and some were unrelated tor_cert errors that
for some reason we had shoved into a tor_bytes::Error.
There is now a separate tor_cert::CertError type, independent from
tor_cert's use of `tor_bytes::Error` for parsing errors.