Implement Clone for all pipeline types (#6653)

# Objective

Pipelines can be customized by wrapping an existing pipeline in a newtype and adding custom logic to its implementation of `SpecializedMeshPipeline::specialize`. To make that easier, the wrapped pipeline type needs to implement `Clone`.

For example, the current non-cloneable pipelines require wrapper pipelines to pull apart the wrapped pipeline like this:

```rust
impl FromWorld for Wireframe2dPipeline {
    fn from_world(world: &mut World) -> Self {
        let p = &world.resource::<Material2dPipeline<ColorMaterial>>();
        Self {
            mesh2d_pipeline: p.mesh2d_pipeline.clone(),
            material2d_layout: p.material2d_layout.clone(),
            vertex_shader: p.vertex_shader.clone(),
            fragment_shader: p.fragment_shader.clone(),
        }
    }
}
```

## Solution

Derive or implement `Clone` on all built-in pipeline types. This is easy to do since they mostly just contain cheaply clonable reference-counted types.

---

## Changelog

Implement `Clone` for all pipeline types.

crates/bevy_pbr/src/material.rs

@@ -232,6 +232,18 @@ pub struct MaterialPipeline<M: Material> {
     marker: PhantomData<M>,
 }
 
+impl<M: Material> Clone for MaterialPipeline<M> {
+    fn clone(&self) -> Self {
+        Self {
+            mesh_pipeline: self.mesh_pipeline.clone(),
+            material_layout: self.material_layout.clone(),
+            vertex_shader: self.vertex_shader.clone(),
+            fragment_shader: self.fragment_shader.clone(),
+            marker: PhantomData,
+        }
+    }
+}
+
 impl<M: Material> SpecializedMeshPipeline for MaterialPipeline<M>
 where
     M::Data: PartialEq + Eq + Hash + Clone,

crates/bevy_pbr/src/render/light.rs

@@ -213,7 +213,7 @@ pub const MAX_UNIFORM_BUFFER_POINT_LIGHTS: usize = 256;
 pub const MAX_DIRECTIONAL_LIGHTS: usize = 10;
 pub const SHADOW_FORMAT: TextureFormat = TextureFormat::Depth32Float;
 
-#[derive(Resource)]
+#[derive(Resource, Clone)]
 pub struct ShadowPipeline {
     pub view_layout: BindGroupLayout,
     pub mesh_layout: BindGroupLayout,

crates/bevy_pbr/src/wireframe.rs

@@ -70,7 +70,7 @@ pub struct WireframeConfig {
     pub global: bool,
 }
 
-#[derive(Resource)]
+#[derive(Resource, Clone)]
 pub struct WireframePipeline {
     mesh_pipeline: MeshPipeline,
     shader: Handle<Shader>,

crates/bevy_sprite/src/mesh2d/material.rs

@@ -218,6 +218,18 @@ where
     }
 }
 
+impl<M: Material2d> Clone for Material2dPipeline<M> {
+    fn clone(&self) -> Self {
+        Self {
+            mesh2d_pipeline: self.mesh2d_pipeline.clone(),
+            material2d_layout: self.material2d_layout.clone(),
+            vertex_shader: self.vertex_shader.clone(),
+            fragment_shader: self.fragment_shader.clone(),
+            marker: PhantomData,
+        }
+    }
+}
+
 impl<M: Material2d> SpecializedMeshPipeline for Material2dPipeline<M>
 where
     M::Data: PartialEq + Eq + Hash + Clone,