Use RenderStartup in MaterialPlugin (#19885)

# Objective

- The MaterialPlugin has some ugly code to initialize some data in the
render world
- #19887

## Solution

- Use the new RenderStartup schedule to use a system instead of using
the plugin `finish()`

## Testing

- Tested that the 3d_scene and shader_material example still work as
expected

crates/bevy_pbr/src/material.rs

@@ -37,6 +37,7 @@ use bevy_render::erased_render_asset::{
 use bevy_render::mesh::mark_3d_meshes_as_changed_if_their_assets_changed;
 use bevy_render::render_asset::{prepare_assets, RenderAssets};
 use bevy_render::renderer::RenderQueue;
+use bevy_render::RenderStartup;
 use bevy_render::{
     batching::gpu_preprocessing::GpuPreprocessingSupport,
     extract_resource::ExtractResource,
@@ -371,7 +372,9 @@ where
         }
 
         if let Some(render_app) = app.get_sub_app_mut(RenderApp) {
-            render_app.add_systems(
+            render_app
+                .add_systems(RenderStartup, setup_render_app::<M>)
+                .add_systems(
                     ExtractSchedule,
                     (
                         extract_mesh_materials::<M>.in_set(MaterialExtractionSystems),
@@ -383,30 +386,24 @@ where
                 );
         }
     }
+}
 
-    fn finish(&self, app: &mut App) {
+fn setup_render_app<M: Material>(
-        let Some(render_app) = app.get_sub_app_mut(RenderApp) else {
+    render_device: Res<RenderDevice>,
-            return;
+    mut bind_group_allocators: ResMut<MaterialBindGroupAllocators>,
-        };
+) {
-
-        render_app.world_mut().resource_scope(
-            |world, mut bind_group_allocators: Mut<MaterialBindGroupAllocators>| {
-                let render_device = world.resource::<RenderDevice>();
     bind_group_allocators.insert(
         TypeId::of::<M>(),
         MaterialBindGroupAllocator::new(
-                        render_device,
+            &render_device,
             M::label(),
-                        material_uses_bindless_resources::<M>(render_device)
+            material_uses_bindless_resources::<M>(&render_device)
                 .then(|| M::bindless_descriptor())
                 .flatten(),
-                        M::bind_group_layout(render_device),
+            M::bind_group_layout(&render_device),
             M::bindless_slot_count(),
         ),
     );
-            },
-        );
-    }
 }
 
 /// A dummy [`AssetId`] that we use as a placeholder whenever a mesh doesn't