chore: add span and log to runtime build (#22064)

crates/tasks/src/runtime.rs

@@ -793,7 +793,9 @@ impl RuntimeBuilder {
     /// The [`TaskManager`] is automatically spawned as a background task that monitors
     /// critical tasks for panics. Use [`Runtime::take_task_manager_handle`] to extract
     /// the join handle if you need to poll for panic errors.
+    #[tracing::instrument(level = "debug", skip_all)]
     pub fn build(self) -> Result<Runtime, RuntimeBuildError> {
+        debug!(?self.config, "Building runtime");
         let config = self.config;
 
         let (owned_runtime, handle) = match &config.tokio {