Sprinkle instrumentation in common crate,in particular in the ecs systems

common/src/path.rs

@@ -1,5 +1,6 @@
 use crate::{
     astar::{Astar, PathResult},
+    span,
     terrain::Block,
     vol::{BaseVol, ReadVol},
 };
@@ -327,6 +328,7 @@ impl Chaser {
     where
         V: BaseVol<Vox = Block> + ReadVol,
     {
+        span!(_guard, "Chaser::chase");
         let pos_to_tgt = pos.distance(tgt);
 
         // If we're already close to the target then there's nothing to do