#[reflect(Default)] for Handle/Mesh2dHandle (#12264)

# Objective

- Make default handles constructible via reflection

## Solution

- Add missing `#[reflect(Default)]` to them

---------

Co-authored-by: Gino Valente <49806985+MrGVSV@users.noreply.github.com>

crates/bevy_asset/src/handle.rs

@@ -3,7 +3,7 @@ use crate::{
     UntypedAssetId,
 };
 use bevy_ecs::prelude::*;
-use bevy_reflect::{Reflect, TypePath};
+use bevy_reflect::{std_traits::ReflectDefault, Reflect, TypePath};
 use bevy_utils::{get_short_name, Uuid};
 use crossbeam_channel::{Receiver, Sender};
 use std::{
@@ -122,7 +122,7 @@ impl std::fmt::Debug for StrongHandle {
 ///
 /// [`Handle::Strong`] also provides access to useful [`Asset`] metadata, such as the [`AssetPath`] (if it exists).
 #[derive(Component, Reflect)]
-#[reflect(Component)]
+#[reflect(Default, Component, Debug, Hash, PartialEq)]
 pub enum Handle<A: Asset> {
     /// A "strong" reference to a live (or loading) [`Asset`]. If a [`Handle`] is [`Handle::Strong`], the [`Asset`] will be kept
     /// alive until the [`Handle`] is dropped. Strong handles also provide access to additional asset metadata.

crates/bevy_sprite/src/mesh2d/mesh.rs

@@ -10,7 +10,7 @@ use bevy_ecs::{
     system::{lifetimeless::*, SystemParamItem, SystemState},
 };
 use bevy_math::{Affine3, Vec4};
-use bevy_reflect::Reflect;
+use bevy_reflect::{std_traits::ReflectDefault, Reflect};
 use bevy_render::mesh::MeshVertexBufferLayoutRef;
 use bevy_render::{
     batching::{
@@ -39,7 +39,7 @@ use crate::Material2dBindGroupId;
 ///
 /// It wraps a [`Handle<Mesh>`] to differentiate from the 3d pipelines which use the handles directly as components
 #[derive(Default, Clone, Component, Debug, Reflect, PartialEq, Eq)]
-#[reflect(Component)]
+#[reflect(Default, Component)]
 pub struct Mesh2dHandle(pub Handle<Mesh>);
 
 impl From<Handle<Mesh>> for Mesh2dHandle {