Derive clone and debug for AssetPlugin (#6583)

# Objective

- Derive Clone and Debug for `AssetPlugin`
- Make it possible to log asset server settings
- And get an owned instance if wrapping `AssetPlugin` in another plugin. See: 129224ef72/src/web_asset_plugin.rs (L45)

crates/bevy_asset/src/lib.rs

@@ -62,6 +62,7 @@ pub enum AssetStage {
 ///
 /// Assets are typed collections with change tracking, which are added as App Resources. Examples of
 /// assets: textures, sounds, 3d models, maps, scenes
+#[derive(Debug, Clone)]
 pub struct AssetPlugin {
     /// The base folder where assets are loaded from, relative to the executable.
     pub asset_folder: String,