Fix meshlet materials (#15755)

# Objective

After #15524, there are these bunny-shaped holes in rendering in the
meshlet example!


![broken](https://github.com/user-attachments/assets/9e9f20ec-b820-44df-b961-68a1dee44002)

This is because (1) they're using a raw asset handle instead of
`MeshMaterial3d`, and (2) the system that extracts mesh materials into
the render world has an unnecessary `With<Mesh3d>` filter, which makes
it not account for meshlets.

## Solution

Remove the redundant filter and use `MeshMaterial3d`. The bunnies got
some paint!


![fixed](https://github.com/user-attachments/assets/adb42556-fd4b-4000-8ca8-1356250dd532)

crates/bevy_pbr/src/material.rs

@@ -550,7 +550,7 @@ pub(super) fn clear_material_instances<M: Material>(
 
 fn extract_mesh_materials<M: Material>(
  mut material_instances: ResMut<RenderMaterialInstances<M>>,
- query: Extract<Query<(Entity, &ViewVisibility, &MeshMaterial3d<M>), With<Mesh3d>>>,
+ query: Extract<Query<(Entity, &ViewVisibility, &MeshMaterial3d<M>)>>,
 ) {
  for (entity, view_visibility, material) in &query {
  if view_visibility.get() {

crates/bevy_pbr/src/meshlet/mod.rs

@@ -55,7 +55,7 @@ use self::{
  },
  visibility_buffer_raster_node::MeshletVisibilityBufferRasterPassNode,
 };
-use crate::{graph::NodePbr, Material};
+use crate::{graph::NodePbr, Material, MeshMaterial3d};
 use bevy_app::{App, Plugin, PostUpdate};
 use bevy_asset::{load_internal_asset, AssetApp, Handle};
 use bevy_core_pipeline::{
@@ -288,7 +288,7 @@ impl Plugin for MeshletPlugin {
 #[derive(Bundle, Clone)]
 pub struct MaterialMeshletMeshBundle<M: Material> {
  pub meshlet_mesh: Handle<MeshletMesh>,
- pub material: Handle<M>,
+ pub material: MeshMaterial3d<M>,
  pub transform: Transform,
  pub global_transform: GlobalTransform,
  /// User indication of whether an entity is visible

examples/3d/meshlet.rs

@@ -86,7 +86,7 @@ fn setup(
  for x in -2..=2 {
  commands.spawn(MaterialMeshletMeshBundle {
  meshlet_mesh: meshlet_mesh_handle.clone(),
- material: standard_materials.add(StandardMaterial {
+ material: MeshMaterial3d(standard_materials.add(StandardMaterial {
  base_color: match x {
  -2 => Srgba::hex("#dc2626").unwrap().into(),
  -1 => Srgba::hex("#ea580c").unwrap().into(),
@@ -97,7 +97,7 @@ fn setup(
  },
  perceptual_roughness: (x + 2) as f32 / 4.0,
  ..default()
- }),
+ })),
  transform: Transform::default()
  .with_scale(Vec3::splat(0.2))
  .with_translation(Vec3::new(x as f32 / 2.0, 0.0, -0.3)),
@@ -107,7 +107,7 @@ fn setup(
  for x in -2..=2 {
  commands.spawn(MaterialMeshletMeshBundle {
  meshlet_mesh: meshlet_mesh_handle.clone(),
- material: debug_material.clone(),
+ material: debug_material.clone().into(),
  transform: Transform::default()
  .with_scale(Vec3::splat(0.2))
  .with_rotation(Quat::from_rotation_y(PI))