Fix sprite picking backend not considering the viewport of the camera. (#16386)

# Objective

- When picking sprites, the pointer is offset from the mouse, causing
you to pick sprites you're not mousing over!

## Solution

- Shift over the cursor by the minimum of the viewport.

## Testing

- I was already using the bevy_mod_picking PR for my project, so it
seems to work!
- I tested this on the sprite_example (making the camera only render to
part of the viewport), and it also works there.

## Notes

- This is just aevyrie/bevy_mod_picking#365 but
in Bevy form.
- We don't need to renormalize the viewport in any way since the
viewport is specified in pixels, so all that matters is that the origin
is correct.

Co-authored-by: johanhelsing <johanhelsing@gmail.com>

Author: 2 people

crates/bevy_sprite/src/picking_backend.rs

@@ -71,8 +71,13 @@ pub fn sprite_picking(
             continue;
         };
 
-        let Ok(cursor_ray_world) = camera.viewport_to_world(cam_transform, location.position)
-        else {
+        let viewport_pos = camera
+            .logical_viewport_rect()
+            .map(|v| v.min)
+            .unwrap_or_default();
+        let pos_in_viewport = location.position - viewport_pos;
+
+        let Ok(cursor_ray_world) = camera.viewport_to_world(cam_transform, pos_in_viewport) else {
             continue;
         };
         let cursor_ray_len = cam_ortho.far - cam_ortho.near;