Move TextureAtlas and friends into bevy_image

[mgi388]

Objective

• Allow other crates to use TextureAtlas and friends without needing to depend on bevy_sprite.
• Specifically, this allows adding TextureAtlas support to custom cursors in Support texture atlases in CustomCursor::Image #17121 by allowing bevy_winit to depend on bevy_image instead of bevy_sprite which is a non-starter.

Solution

• Move TextureAtlas, TextureAtlasBuilder, TextureAtlasSources, TextureAtlasLayout and DynamicTextureAtlasBuilder into bevy_image.
• Add a new plugin to bevy_image named TextureAtlasPlugin which allows us to register TextureAtlas and TextureAtlasLayout which was previously done in SpritePlugin. Since SpritePlugin did the registration previously, we just need to make it add TextureAtlasPlugin.

Testing

• CI builds it.
• I also ran multiple examples which hopefully covered any issues:

$ cargo run --example sprite
$ cargo run --example text
$ cargo run --example ui_texture_atlas
$ cargo run --example sprite_animation
$ cargo run --example sprite_sheet
$ cargo run --example sprite_picking

---

Migration Guide

The following types have been moved from bevy_sprite to bevy_image: TextureAtlas, TextureAtlasBuilder, TextureAtlasSources, TextureAtlasLayout and DynamicTextureAtlasBuilder.

If you are using the bevy crate, and were importing these types directly (e.g. before use bevy::sprite::TextureAtlas), be sure to update your import paths (e.g. after use bevy::image::TextureAtlas)

If you are using the bevy prelude to import these types (e.g. use bevy::prelude::*), you don't need to change anything.

If you are using the bevy_sprite subcrate, be sure to add bevy_image as a dependency if you do not already have it, and be sure to update your import paths.

[ickshonpe]

I'd like to remove the bevy_sprite dependency from bevy_ui completely as well, this seems like a good first step.

Don't see any problems with these changes, all the examples still work fine.