Activate missing-docs warning for `bevy_sprite` (#24490)

# Objective

Enable the lint missing-docs, crate by crate (see #3492)

## Solution

- Add docs where needed
- Add specific exceptions where needed
- In the process, found that `bevy_sprite` and `bevy_sprite_render` have
identical but distinct system set enums, but only `bevy_sprite_render`
uses its definition. This struck me as a bit of a footgun (users
ordering systems against the `bevy_sprite` one will fail to order
against any actual systems), so I deleted the one in `bevy_sprite`.

## Testing

Ran `cargo test --doc` for luck.