Cleanup render schedule (bevyengine#7589)

# Objective

- Fixes bevyengine#7531

## Solution

- Add systems to prepare set
- Also remove a unnecessary apply_systems_buffers from ExtractCommands set.

crates/bevy_pbr/src/lib.rs

@@ -284,6 +284,7 @@ impl Plugin for PbrPlugin {
  // because prepare_lights creates new views for shadow mapping
  .add_system(
  apply_system_buffers
+ .in_set(RenderSet::Prepare)
  .after(RenderLightSystems::PrepareLights)
  .before(ViewSet::PrepareUniforms),
  )

crates/bevy_pbr/src/material.rs

@@ -194,7 +194,11 @@ where
  .init_resource::<RenderMaterials<M>>()
  .init_resource::<SpecializedMeshPipelines<MaterialPipeline<M>>>()
  .add_system_to_schedule(ExtractSchedule, extract_materials::<M>)
- .add_system(prepare_materials::<M>.after(PrepareAssetLabel::PreAssetPrepare))
+ .add_system(
+ prepare_materials::<M>
+ .in_set(RenderSet::Prepare)
+ .after(PrepareAssetLabel::PreAssetPrepare),
+ )
  .add_system(queue_material_meshes::<M>.in_set(RenderSet::Queue));
  }
 

crates/bevy_render/src/lib.rs

@@ -109,7 +109,6 @@ impl RenderSet {
  let mut schedule = Schedule::new();
 
  // Create "stage-like" structure using buffer flushes + ordering
- schedule.add_system(apply_system_buffers.in_set(ExtractCommands));
  schedule.add_system(apply_system_buffers.in_set(PrepareFlush));
  schedule.add_system(apply_system_buffers.in_set(QueueFlush));
  schedule.add_system(apply_system_buffers.in_set(PhaseSortFlush));

crates/bevy_sprite/src/mesh2d/material.rs

@@ -162,8 +162,8 @@ where
  .add_system_to_schedule(ExtractSchedule, extract_materials_2d::<M>)
  .add_system(
  prepare_materials_2d::<M>
- .after(PrepareAssetLabel::PreAssetPrepare)
- .in_set(RenderSet::Prepare),
+ .in_set(RenderSet::Prepare)
+ .after(PrepareAssetLabel::PreAssetPrepare),
  )
  .add_system(queue_material2d_meshes::<M>.in_set(RenderSet::Queue));
  }