Run observers before hooks for on_replace and on_remove (bevyengine#16499)

# Objective

- Fixes bevyengine#16498 

## Solution

- Trivially swaps ordering of hooks and observers for all call sites
where they are triggered for `on_replace` or `on_remove`

## Testing

- Just CI

---

## Migration Guide

The order of hooks and observers for `on_replace` and `on_remove` has
been swapped. Observers are now run before hooks. This is a more natural
ordering where the removal ordering is inverted compared to the
insertion ordering.

Author: nakedible

crates/bevy_ecs/src/bundle.rs

@@ -902,14 +902,14 @@ impl<'w> BundleInserter<'w> {
             let mut deferred_world = self.world.into_deferred();
 
             if insert_mode == InsertMode::Replace {
-                deferred_world.trigger_on_replace(archetype, entity, add_bundle.iter_existing());
                 if archetype.has_replace_observer() {
                     deferred_world.trigger_observers(
                         ON_REPLACE,
                         entity,
                         add_bundle.iter_existing(),
                     );
                 }
+                deferred_world.trigger_on_replace(archetype, entity, add_bundle.iter_existing());
             }
         }
 

crates/bevy_ecs/src/world/entity_ref.rs

@@ -1863,14 +1863,14 @@ impl<'w> EntityWorldMut<'w> {
 
         // SAFETY: All components in the archetype exist in world
         unsafe {
-            deferred_world.trigger_on_replace(archetype, self.entity, archetype.components());
             if archetype.has_replace_observer() {
                 deferred_world.trigger_observers(ON_REPLACE, self.entity, archetype.components());
             }
-            deferred_world.trigger_on_remove(archetype, self.entity, archetype.components());
+            deferred_world.trigger_on_replace(archetype, self.entity, archetype.components());
             if archetype.has_remove_observer() {
                 deferred_world.trigger_observers(ON_REMOVE, self.entity, archetype.components());
             }
+            deferred_world.trigger_on_remove(archetype, self.entity, archetype.components());
         }
 
         for component_id in archetype.components() {
@@ -2118,18 +2118,18 @@ unsafe fn trigger_on_replace_and_on_remove_hooks_and_observers(
     entity: Entity,
     bundle_info: &BundleInfo,
 ) {
-    deferred_world.trigger_on_replace(archetype, entity, bundle_info.iter_explicit_components());
     if archetype.has_replace_observer() {
         deferred_world.trigger_observers(
             ON_REPLACE,
             entity,
             bundle_info.iter_explicit_components(),
         );
     }
-    deferred_world.trigger_on_remove(archetype, entity, bundle_info.iter_explicit_components());
+    deferred_world.trigger_on_replace(archetype, entity, bundle_info.iter_explicit_components());
     if archetype.has_remove_observer() {
         deferred_world.trigger_observers(ON_REMOVE, entity, bundle_info.iter_explicit_components());
     }
+    deferred_world.trigger_on_remove(archetype, entity, bundle_info.iter_explicit_components());
 }
 
 const QUERY_MISMATCH_ERROR: &str = "Query does not match the current entity";
@@ -4910,14 +4910,14 @@ mod tests {
             "OrdB hook on_insert",
             "OrdB observer on_insert",
             "OrdB command on_add", // command added by OrdB hook on_add, needs to run before despawn command
-            "OrdA hook on_replace", // start of despawn
-            "OrdB hook on_replace",
-            "OrdA observer on_replace",
+            "OrdA observer on_replace", // start of despawn
             "OrdB observer on_replace",
-            "OrdA hook on_remove",
-            "OrdB hook on_remove",
+            "OrdA hook on_replace",
+            "OrdB hook on_replace",
             "OrdA observer on_remove",
             "OrdB observer on_remove",
+            "OrdA hook on_remove",
+            "OrdB hook on_remove",
         ];
         world.flush();
         assert_eq!(world.resource_mut::<TestVec>().0.as_slice(), &expected[..]);