feat(tvix/tracing): introduce common tvix-tracing crate

Introduce a new common crate that contains tracing boilerplate which then
can be used in the cli, tvix-store and tvix-build crates.
It has otlp as an optional feature, which is currently only used by
tvix-store.

Change-Id: I41468ac4d9c65174515d721513b96fea463d6ed2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11758
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: Simon Hauser <simon.hauser@helsinki-systems.de>

tvix/Cargo.toml

@@ -28,6 +28,7 @@ members = [
   "nix-compat",
   "serde",
   "store",
+  "tracing",
 ]
 
 [workspace.lints.clippy]