Add a tracing span for run criteria. (bevyengine#4709)

# Objective

Adds a tracing span for run critieria.

This change will be invalidated by stageless, but it was a simple change.

Fixes bevyengine#4681.

## Changelog

Shows how long a run criteria takes to run when tracing is enabled.
![image](https://user-images.githubusercontent.com/2180432/167517447-93dba7db-8c85-4686-90e0-30e9636f120f.png)

Author: hymm

crates/bevy_ecs/src/schedule/stage.rs

@@ -802,6 +802,12 @@ impl Stage for SystemStage {
             for index in 0..self.run_criteria.len() {
                 let (run_criteria, tail) = self.run_criteria.split_at_mut(index);
                 let mut criteria = &mut tail[0];
+
+                #[cfg(feature = "trace")]
+                let _span =
+                    bevy_utils::tracing::info_span!("run criteria", name = &*criteria.name())
+                        .entered();
+
                 match &mut criteria.inner {
                     RunCriteriaInner::Single(system) => criteria.should_run = system.run((), world),
                     RunCriteriaInner::Piped {