chore(ls): add assertion for ancestor count

Tests for the resource leak without major refactorings.

Author: Alonely0

src/uu/ls/src/ls.rs

@@ -1253,6 +1253,7 @@ pub fn list_with_output<O: LsOutput>(
             &mut entries,
         )?;
         listed_ancestors.remove(&inode);
+        debug_assert!(listed_ancestors.is_empty());
     }
 
     output.finalize(config)?;