allow EntityCloner to move components without Clone or Reflect (#20065)

# Objective
Fix #18079 

## Solution
- `EntityCloner` can now move components that don't have `Clone` or
`Reflect` implementation.
- Components with `ComponentCloneBehavior::Ignore` will not be moved.
- Components with `ComponentCloneBehavior::Custom` will be cloned using
their defined `ComponentCloneFn` and then removed from the source entity
to respect their `queue_deferred` logic.
- Relationships still need to be `Clone` or `Reflect` to be movable.
- Custom relationship data is now correctly preserved when cloned or
moved using `EntityCloner`.

## Testing
- Added new tests for moving components

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>

Author: eugineerd

crates/bevy_ecs/macros/src/component.rs

@@ -293,8 +293,14 @@ pub fn derive_component(input: TokenStream) -> TokenStream {
         .then_some(quote! { #bevy_ecs_path::component::Immutable })
         .unwrap_or(quote! { #bevy_ecs_path::component::Mutable });
 
-    let clone_behavior = if relationship_target.is_some() {
-        quote!(#bevy_ecs_path::component::ComponentCloneBehavior::Custom(#bevy_ecs_path::relationship::clone_relationship_target::<Self>))
+    let clone_behavior = if relationship_target.is_some() || relationship.is_some() {
+        quote!(
+            use #bevy_ecs_path::relationship::{
+                RelationshipCloneBehaviorBase, RelationshipCloneBehaviorViaClone, RelationshipCloneBehaviorViaReflect,
+                RelationshipTargetCloneBehaviorViaClone, RelationshipTargetCloneBehaviorViaReflect, RelationshipTargetCloneBehaviorHierarchy
+                };
+            (&&&&&&&#bevy_ecs_path::relationship::RelationshipCloneBehaviorSpecialization::<Self>::default()).default_clone_behavior()
+        )
     } else if let Some(behavior) = attrs.clone_behavior {
         quote!(#bevy_ecs_path::component::ComponentCloneBehavior::#behavior)
     } else {

crates/bevy_ecs/src/bundle/remove.rs

@@ -22,6 +22,7 @@ pub(crate) struct BundleRemover<'w> {
     old_and_new_table: Option<(NonNull<Table>, NonNull<Table>)>,
     old_archetype: NonNull<Archetype>,
     new_archetype: NonNull<Archetype>,
+    pub(crate) relationship_hook_mode: RelationshipHookMode,
 }
 
 impl<'w> BundleRemover<'w> {
@@ -97,6 +98,7 @@ impl<'w> BundleRemover<'w> {
             old_archetype: old_archetype.into(),
             old_and_new_table: tables,
             world: world.as_unsafe_world_cell(),
+            relationship_hook_mode: RelationshipHookMode::Run,
         };
         if is_new_created {
             remover
@@ -160,7 +162,7 @@ impl<'w> BundleRemover<'w> {
                 entity,
                 bundle_components_in_archetype(),
                 caller,
-                RelationshipHookMode::Run,
+                self.relationship_hook_mode,
             );
             if self.old_archetype.as_ref().has_remove_observer() {
                 deferred_world.trigger_observers(

crates/bevy_ecs/src/component/clone.rs

@@ -3,16 +3,16 @@ use core::marker::PhantomData;
 use crate::component::Component;
 use crate::entity::{ComponentCloneCtx, SourceComponent};
 
-/// Function type that can be used to clone an entity.
+/// Function type that can be used to clone a component of an entity.
 pub type ComponentCloneFn = fn(&SourceComponent, &mut ComponentCloneCtx);
 
-/// The clone behavior to use when cloning a [`Component`].
+/// The clone behavior to use when cloning or moving a [`Component`].
 #[derive(Clone, Debug, Default, PartialEq, Eq)]
 pub enum ComponentCloneBehavior {
     /// Uses the default behavior (which is passed to [`ComponentCloneBehavior::resolve`])
     #[default]
     Default,
-    /// Do not clone this component.
+    /// Do not clone/move this component.
     Ignore,
     /// Uses a custom [`ComponentCloneFn`].
     Custom(ComponentCloneFn),