Fix some doc warnings

[ameknite]

Objective

• Fix some doc warnings
• Add doc-scrape-examples to all examples

Moved from #12692

I run cargo +nightly doc --workspace --all-features --no-deps -Zunstable-options -Zrustdoc-scrape-examples

warning: public documentation for `GzAssetLoaderError` links to private item `GzAssetLoader`
  --> examples/asset/asset_decompression.rs:24:47
   |
24 | /// Possible errors that can be produced by [`GzAssetLoader`]
   |                                               ^^^^^^^^^^^^^ this item is private
   |
   = note: this link will resolve properly if you pass `--document-private-items`
   = note: `#[warn(rustdoc::private_intra_doc_links)]` on by default

warning: `bevy` (example "asset_decompression") generated 1 warning
warning: unresolved link to `shape::Quad`
 --> examples/2d/mesh2d.rs:3:15
  |
3 | //! [`Quad`]: shape::Quad
  |               ^^^^^^^^^^^ no item named `shape` in scope
  |
  = note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default

warning: `bevy` (example "mesh2d") generated 1 warning
warning: unresolved link to `WorldQuery`
 --> examples/ecs/custom_query_param.rs:1:49
  |
1 | //! This example illustrates the usage of the [`WorldQuery`] derive macro, which allows
  |                                                 ^^^^^^^^^^ no item named `WorldQuery` in scope
  |
  = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
  = note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default

warning: `bevy` (example "custom_query_param") generated 1 warning
warning: unresolved link to `shape::Quad`
 --> examples/2d/mesh2d_vertex_color_texture.rs:4:15
  |
4 | //! [`Quad`]: shape::Quad
  |               ^^^^^^^^^^^ no item named `shape` in scope
  |
  = note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default

warning: `bevy` (example "mesh2d_vertex_color_texture") generated 1 warning
warning: public documentation for `TextPlugin` links to private item `CoolText`
  --> examples/asset/processing/asset_processing.rs:48:9
   |
48 | /// * [`CoolText`]: a custom RON text format that supports dependencies and embedded dependencies
   |         ^^^^^^^^ this item is private
   |
   = note: this link will resolve properly if you pass `--document-private-items`
   = note: `#[warn(rustdoc::private_intra_doc_links)]` on by default

warning: public documentation for `TextPlugin` links to private item `Text`
  --> examples/asset/processing/asset_processing.rs:49:9
   |
49 | /// * [`Text`]: a "normal" plain text file
   |         ^^^^ this item is private
   |
   = note: this link will resolve properly if you pass `--document-private-items`

warning: public documentation for `TextPlugin` links to private item `CoolText`
  --> examples/asset/processing/asset_processing.rs:51:57
   |
51 | /// It also defines an asset processor that will load [`CoolText`], resolve embedded dependenc...
   |                                                         ^^^^^^^^ this item is private
   |
   = note: this link will resolve properly if you pass `--document-private-items`

warning: `bevy` (example "asset_processing") generated 3 warnings
warning: public documentation for `CustomAssetLoaderError` links to private item `CustomAssetLoader`
  --> examples/asset/custom_asset.rs:20:47
   |
20 | /// Possible errors that can be produced by [`CustomAssetLoader`]
   |                                               ^^^^^^^^^^^^^^^^^ this item is private
   |
   = note: this link will resolve properly if you pass `--document-private-items`
   = note: `#[warn(rustdoc::private_intra_doc_links)]` on by default

warning: public documentation for `BlobAssetLoaderError` links to private item `CustomAssetLoader`
  --> examples/asset/custom_asset.rs:61:47
   |
61 | /// Possible errors that can be produced by [`CustomAssetLoader`]
   |                                               ^^^^^^^^^^^^^^^^^ this item is private
   |
   = note: this link will resolve properly if you pass `--document-private-items`

warning: `bevy` (example "mesh2d") generated 1 warning
warning: public documentation for `log_layers_ecs` links to private item `update_subscriber`
 --> examples/app/log_layers_ecs.rs:6:18
  |
6 | //! Inside the [`update_subscriber`] function we will create a [`mpsc::Sender`] and a [`mpsc::R...
  |                  ^^^^^^^^^^^^^^^^^ this item is private
  |
  = note: this link will resolve properly if you pass `--document-private-items`
  = note: `#[warn(rustdoc::private_intra_doc_links)]` on by default

warning: unresolved link to `AdvancedLayer`
 --> examples/app/log_layers_ecs.rs:7:72
  |
7 | ... will go into the [`AdvancedLayer`] and the [`Receiver`](mpsc::Receiver) will
  |                        ^^^^^^^^^^^^^ no item named `AdvancedLayer` in scope
  |
  = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
  = note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default

warning: unresolved link to `LogEvents`
 --> examples/app/log_layers_ecs.rs:8:42
  |
8 | //! go into a non-send resource called [`LogEvents`] (It has to be non-send because [`Receiver`...
  |                                          ^^^^^^^^^ no item named `LogEvents` in scope
  |
  = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`

warning: public documentation for `log_layers_ecs` links to private item `transfer_log_events`
 --> examples/app/log_layers_ecs.rs:9:30
  |
9 | //! From there we will use [`transfer_log_events`] to transfer log events from [`LogEvents`] to...
  |                              ^^^^^^^^^^^^^^^^^^^ this item is private
  |
  = note: this link will resolve properly if you pass `--document-private-items`

warning: unresolved link to `LogEvents`
 --> examples/app/log_layers_ecs.rs:9:82
  |
9 | ...nsfer log events from [`LogEvents`] to an ECS event called [`LogEvent`].
  |                            ^^^^^^^^^ no item named `LogEvents` in scope
  |
  = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`

warning: public documentation for `log_layers_ecs` links to private item `LogEvent`
 --> examples/app/log_layers_ecs.rs:9:119
  |
9 | ...nts`] to an ECS event called [`LogEvent`].
  |                                   ^^^^^^^^ this item is private
  |
  = note: this link will resolve properly if you pass `--document-private-items`

warning: public documentation for `log_layers_ecs` links to private item `LogEvent`
  --> examples/app/log_layers_ecs.rs:11:49
   |
11 | //! Finally, after all that we can access the [`LogEvent`] event from our systems and use it.
   |                                                 ^^^^^^^^ this item is private
   |
   = note: this link will resolve properly if you pass `--document-private-items`