feat(tvix/tracing): optional progressbar

Disable the progressbar on default and provide a interface for
optionally enabling the progressbar.

Change-Id: I0e31b1957e80cf64a8dcf65c6ceb3713975b8220
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11861
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: Simon Hauser <simon.hauser@helsinki-systems.de>

tvix/cli/src/main.rs

@@ -281,6 +281,7 @@ fn main() {
 
     let _ = tvix_tracing::TracingBuilder::default()
         .level(args.log_level)
+        .enable_progressbar()
         .build()
         .expect("unable to set up tracing subscriber");
     let tokio_runtime = tokio::runtime::Runtime::new().expect("failed to setup tokio runtime");