feat(tvix/cli): add toplevel progress span

This gives some better feedback something is going on, gives a (named)
root for all the progress children we're drawing, and also counts the
time we are in eval.

Change-Id: Ibe81dcebf0a2b59bb0680da62e206eb5270f9d3c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11798
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: aspen <root@gws.fyi>

tvix/cli/Cargo.toml

@@ -23,6 +23,7 @@ rnix = "0.11.0"
 thiserror = "1.0.38"
 tokio = "1.28.0"
 tracing = "0.1.40"
+tracing-indicatif = "0.3.6"
 
 [dependencies.wu-manber]
 git = "https://github.com/tvlfyi/wu-manber.git"