Rename Add to Queue for methods with deferred semantics (#15234)

# Objective

- Fixes #15106

## Solution

- Trivial refactor to rename the method. The duplicate method `push` was
removed as well. This will simpify the API and make the semantics more
clear. `Add` implies that the action happens immediately, whereas in
reality, the command is queued to be run eventually.
- `ChildBuilder::add_command` has similarly been renamed to
`queue_command`.

## Testing

Unit tests should suffice for this simple refactor.

---

## Migration Guide

- `Commands::add` and `Commands::push` have been replaced with
`Commnads::queue`.
- `ChildBuilder::add_command` has been renamed to
`ChildBuilder::queue_command`.

Author: BenjaminBrienen

benches/benches/bevy_ecs/world/commands.rs

@@ -146,9 +146,9 @@ pub fn fake_commands(criterion: &mut Criterion) {
                 let mut commands = Commands::new(&mut command_queue, &world);
                 for i in 0..command_count {
                     if black_box(i % 2 == 0) {
-                        commands.add(FakeCommandA);
+                        commands.queue(FakeCommandA);
                     } else {
-                        commands.add(FakeCommandB(0));
+                        commands.queue(FakeCommandB(0));
                     }
                 }
                 command_queue.apply(&mut world);
@@ -190,7 +190,7 @@ pub fn sized_commands_impl<T: Default + Command>(criterion: &mut Criterion) {
             bencher.iter(|| {
                 let mut commands = Commands::new(&mut command_queue, &world);
                 for _ in 0..command_count {
-                    commands.add(T::default());
+                    commands.queue(T::default());
                 }
                 command_queue.apply(&mut world);
             });

crates/bevy_ecs/src/event/writer.rs

@@ -51,7 +51,7 @@ use bevy_ecs::{
 ///     //
 ///     // NOTE: the event won't actually be sent until commands get applied during
 ///     // apply_deferred.
-///     commands.add(|w: &mut World| {
+///     commands.queue(|w: &mut World| {
 ///         w.send_event(MyEvent);
 ///     });
 /// }

crates/bevy_ecs/src/observer/mod.rs

@@ -830,7 +830,7 @@ mod tests {
             ..Default::default()
         });
 
-        world.commands().add(
+        world.commands().queue(
             // SAFETY: we registered `event_a` above and it matches the type of TriggerA
             unsafe { EmitDynamicTrigger::new_with_id(event_a, EventA, ()) },
         );

crates/bevy_ecs/src/observer/runner.rs

@@ -65,7 +65,7 @@ impl Component for ObserverState {
 
     fn register_component_hooks(hooks: &mut ComponentHooks) {
         hooks.on_add(|mut world, entity, _| {
-            world.commands().add(move |world: &mut World| {
+            world.commands().queue(move |world: &mut World| {
                 world.register_observer(entity);
             });
         });
@@ -78,7 +78,7 @@ impl Component for ObserverState {
                     .as_mut()
                     .descriptor,
             );
-            world.commands().add(move |world: &mut World| {
+            world.commands().queue(move |world: &mut World| {
                 world.unregister_observer(entity, descriptor);
             });
         });
@@ -398,7 +398,7 @@ fn hook_on_add<E: Event, B: Bundle, S: ObserverSystem<E, B>>(
     entity: Entity,
     _: ComponentId,
 ) {
-    world.commands().add(move |world: &mut World| {
+    world.commands().queue(move |world: &mut World| {
         let event_type = world.init_component::<E>();
         let mut components = Vec::new();
         B::component_ids(&mut world.components, &mut world.storages, &mut |id| {

crates/bevy_ecs/src/reflect/entity_commands.rs

@@ -79,7 +79,7 @@ pub trait ReflectCommandExt {
     ///
     ///     // Or even with BundleA
     ///     prefab.data = boxed_reflect_bundle_a;
-    ///     
+    ///
     ///     // No matter which component or bundle is in the resource and without knowing the exact type, you can
     ///     // use the insert_reflect entity command to insert that component/bundle into an entity.
     ///     commands
@@ -174,7 +174,7 @@ pub trait ReflectCommandExt {
 
 impl ReflectCommandExt for EntityCommands<'_> {
     fn insert_reflect(&mut self, component: Box<dyn PartialReflect>) -> &mut Self {
-        self.commands.add(InsertReflect {
+        self.commands.queue(InsertReflect {
             entity: self.entity,
             component,
         });
@@ -185,7 +185,7 @@ impl ReflectCommandExt for EntityCommands<'_> {
         &mut self,
         component: Box<dyn PartialReflect>,
     ) -> &mut Self {
-        self.commands.add(InsertReflectWithRegistry::<T> {
+        self.commands.queue(InsertReflectWithRegistry::<T> {
             entity: self.entity,
             _t: PhantomData,
             component,
@@ -194,7 +194,7 @@ impl ReflectCommandExt for EntityCommands<'_> {
     }
 
     fn remove_reflect(&mut self, component_type_path: impl Into<Cow<'static, str>>) -> &mut Self {
-        self.commands.add(RemoveReflect {
+        self.commands.queue(RemoveReflect {
             entity: self.entity,
             component_type_path: component_type_path.into(),
         });
@@ -205,7 +205,7 @@ impl ReflectCommandExt for EntityCommands<'_> {
         &mut self,
         component_type_name: impl Into<Cow<'static, str>>,
     ) -> &mut Self {
-        self.commands.add(RemoveReflectWithRegistry::<T> {
+        self.commands.queue(RemoveReflectWithRegistry::<T> {
             entity: self.entity,
             _t: PhantomData,
             component_type_name: component_type_name.into(),