Add tracing / tracing_subscriber to make logging easier

[marcua]

• After comparing log, slog, and tracing, it seems like tracing might have an interface as simple as log but be slightly more future-forward.
• The tracing_subscriber json feature seems like a good place to start: structured logging as JSONL
• One thing to figure out: for the libraries that rely on log, is there a way to still log them without needing to run env_logger::init() in addition to whatever tracing init I do?
• Start by adding tracing to the snapshots code, which has pretty gnarly printlns

It seems like I start here

        let filter = EnvFilter::try_from_default_env().unwrap_or_else(|_| EnvFilter::new("info"));
        tracing_subscriber::fmt()
            .with_writer(file) // Optional
            .with_env_filter(filter)
            .with_max_level(Level::TRACE)
            .init();
        let work_span = span!(Level::TRACE, "work", task = "processing data");
        let _enter = work_span.enter();
        debug!("yak shaved successfully", user = "marcua");