Make the component types of the new animation players clonable. (#13736)

# Objective

Some use cases might require holding onto the previous state of the
animation player for change detection.

## Solution

Added `clone` and `copy` implementation to most animation types. 
Added optimized `clone_from` implementations for the specific use case
of holding a `PreviousAnimationPlayer` component.

---------

Co-authored-by: Alice Cecile <[email protected]>

Author: mintlu8

crates/bevy_animation/src/lib.rs

@@ -236,7 +236,7 @@ impl Hash for AnimationTargetId {
 /// Note that each entity can only be animated by one animation player at a
 /// time. However, you can change [`AnimationTarget`]'s `player` property at
 /// runtime to change which player is responsible for animating the entity.
-#[derive(Clone, Component, Reflect)]
+#[derive(Clone, Copy, Component, Reflect)]
 #[reflect(Component, MapEntities)]
 pub struct AnimationTarget {
     /// The ID of this animation target.
@@ -326,7 +326,7 @@ pub enum RepeatAnimation {
 /// playing, but is presently paused.
 ///
 /// An stopped animation is considered no longer active.
-#[derive(Debug, Reflect)]
+#[derive(Debug, Clone, Copy, Reflect)]
 pub struct ActiveAnimation {
     /// The factor by which the weight from the [`AnimationGraph`] is multiplied.
     weight: f32,
@@ -515,6 +515,21 @@ pub struct AnimationPlayer {
     blend_weights: HashMap<AnimationNodeIndex, f32>,
 }
 
+// This is needed since `#[derive(Clone)]` does not generate optimized `clone_from`.
+impl Clone for AnimationPlayer {
+    fn clone(&self) -> Self {
+        Self {
+            active_animations: self.active_animations.clone(),
+            blend_weights: self.blend_weights.clone(),
+        }
+    }
+
+    fn clone_from(&mut self, source: &Self) {
+        self.active_animations.clone_from(&source.active_animations);
+        self.blend_weights.clone_from(&source.blend_weights);
+    }
+}
+
 /// The components that we might need to read or write during animation of each
 /// animation target.
 struct AnimationTargetContext<'a> {

crates/bevy_animation/src/transition.rs

@@ -33,8 +33,23 @@ pub struct AnimationTransitions {
     transitions: Vec<AnimationTransition>,
 }
 
+// This is needed since `#[derive(Clone)]` does not generate optimized `clone_from`.
+impl Clone for AnimationTransitions {
+    fn clone(&self) -> Self {
+        Self {
+            main_animation: self.main_animation,
+            transitions: self.transitions.clone(),
+        }
+    }
+
+    fn clone_from(&mut self, source: &Self) {
+        self.main_animation = source.main_animation;
+        self.transitions.clone_from(&source.transitions);
+    }
+}
+
 /// An animation that is being faded out as part of a transition
-#[derive(Debug, Reflect)]
+#[derive(Debug, Clone, Copy, Reflect)]
 pub struct AnimationTransition {
     /// The current weight. Starts at 1.0 and goes to 0.0 during the fade-out.
     current_weight: f32,