Fix footgunny MeshPlugin export (#21254)

# Objective

- Fixes #21253, see that issue
for details
- The `MeshPlugin` that was *wrongly* used per that issue is now
`MeshRenderAssetPlugin`, given that it deals with `RenderAsset`s.
- Note that we cannot name it `MeshRenderPlugin`, as [that name is also
already
taken](https://dev-docs.bevy.org/bevy/pbr/struct.MeshRenderPlugin.html)
- We now have `MeshPlugin`, `MeshRenderPlugin`, `MeshRenderAssetPlugin`,
and `Mesh2dRenderPlugin`, ALL of which are in different crates :bavy:
:bavy: :bavy:
- Since this is an implementation detail, I think we could also make it
`pub(crate)`. I verified that that compiles fine. But I'll leave that
decision for someone who knows the rendering architecture better.
- Also fixed a subtle mistake in asset initialization I spotted while on
it, as the proper `MeshPlugin` forgets to initialize skinned mesh bind
poses.
- Funnily enough, the CI caught this, as before this change our own glTF
tests accidentally used the *wrong* `MeshPlugin` lol
- Fixes wrong documentation on the rendering plugin
- No need for a migration guide, this is already documented in
https://github.com/bevyengine/bevy/blob/release-0.17.0/release-content/migration-guides/bevy_render_reorganization.md

Author: janhohenheim

crates/bevy_gltf/src/loader/mod.rs

@@ -1909,7 +1909,7 @@ mod test {
     use bevy_ecs::{resource::Resource, world::World};
     use bevy_log::LogPlugin;
     use bevy_mesh::skinning::SkinnedMeshInverseBindposes;
-    use bevy_render::mesh::MeshPlugin;
+    use bevy_mesh::MeshPlugin;
     use bevy_scene::ScenePlugin;
 
     fn test_app(dir: Dir) -> App {

crates/bevy_mesh/src/lib.rs

@@ -45,12 +45,14 @@ bitflags! {
     }
 }
 
+/// Adds [`Mesh`] as an asset.
 #[derive(Default)]
 pub struct MeshPlugin;
 
 impl Plugin for MeshPlugin {
     fn build(&self, app: &mut App) {
         app.init_asset::<Mesh>()
+            .init_asset::<skinning::SkinnedMeshInverseBindposes>()
             .register_asset_reflect::<Mesh>()
             .add_systems(
                 PostUpdate,

crates/bevy_render/src/lib.rs

@@ -79,7 +79,7 @@ pub use extract_param::Extract;
 use crate::{
     camera::CameraPlugin,
     gpu_readback::GpuReadbackPlugin,
-    mesh::{MeshPlugin, MorphPlugin, RenderMesh},
+    mesh::{MeshRenderAssetPlugin, MorphPlugin, RenderMesh},
     render_asset::prepare_assets,
     render_resource::{init_empty_bind_group_layout, PipelineCache},
     renderer::{render_system, RenderAdapterInfo},
@@ -366,7 +366,7 @@ impl Plugin for RenderPlugin {
             WindowRenderPlugin,
             CameraPlugin,
             ViewPlugin,
-            MeshPlugin,
+            MeshRenderAssetPlugin,
             GlobalsPlugin,
             MorphPlugin,
             TexturePlugin,

crates/bevy_render/src/mesh/mod.rs

@@ -7,7 +7,7 @@ use crate::{
 };
 use allocator::MeshAllocatorPlugin;
 use bevy_app::{App, Plugin, PostUpdate};
-use bevy_asset::{AssetApp, AssetId, RenderAssetUsages};
+use bevy_asset::{AssetId, RenderAssetUsages};
 use bevy_ecs::{
     prelude::*,
     system::{
@@ -19,12 +19,13 @@ use bevy_mesh::morph::{MeshMorphWeights, MorphWeights};
 use bevy_mesh::*;
 use wgpu::IndexFormat;
 
-/// Adds the [`Mesh`] as an asset and makes sure that they are extracted and prepared for the GPU.
-pub struct MeshPlugin;
+/// Makes sure that [`Mesh`]es are extracted and prepared for the GPU.
+/// Does *not* add the [`Mesh`] as an asset. Use [`MeshPlugin`] for that.
+pub struct MeshRenderAssetPlugin;
 
-impl Plugin for MeshPlugin {
+impl Plugin for MeshRenderAssetPlugin {
     fn build(&self, app: &mut App) {
-        app.init_asset::<skinning::SkinnedMeshInverseBindposes>()
+        app
             // 'Mesh' must be prepared after 'Image' as meshes rely on the morph target image being ready
             .add_plugins(RenderAssetPlugin::<RenderMesh, GpuImage>::default())
             .add_plugins(MeshAllocatorPlugin);