build: migrate tokio console control to build.rs

Instead of relying on dirty-ing a checked in file (.cargo/config.toml),
switch to a feature flag based flow to enable the tokio debug console.
This avoids accidental thrashing in the checked in file. It also allows
a discoverable path from the justfile for new developers.

Cargo.toml

@@ -47,6 +47,7 @@ database = ["rusqlite"]
 dns = []
 tor = ["arti-client", "tor-rtcompat"]
 filter-control = []
+tokio-console = []
 
 [dev-dependencies]
 corepc-node = { version = "0.5.0", default-features = false, features = [

build.rs

@@ -0,0 +1,4 @@
+fn main() {
+    #[cfg(feature = "tokio-console")]
+    println!("cargo:rustc-cfg=tokio_unstable");
+}

justfile

@@ -4,6 +4,10 @@ default:
 build:
   cargo build
 
+# Run with the tokio console enabled for verbose debugging.
+run-with-console:
+  cargo run --features tokio-console
+
 check:
    cargo fmt
    cargo clippy --all-targets