please redirect logging metadata to stderr

[jonassmedegaard]

tracing-subscriber by default sends logging information to stdout, which interferes with program data.

Please consider adjusting to send logging information to stderr instead.

For inspiration you can see this patch applied for Debian packaging of sdml (reason I say "for inspiration" is that the patch also covers another issue which you might not care about: Debian does not include the EnvFilter to avoid maintaining multiple branches of regex-automata).