bevy_sprite picking backend does not honor render layers

[coreh]

Bevy version

0.15

What you did

Create multiple sprites, multiple cameras, selectively render some of the sprites in some of the cameras using render layers. Use bevy_picking.

What went wrong

Sprites are picked across all cameras (that have the window as a render target) regardless of render layers.

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(Also, if #16886 is merged, this should probably also apply to that.)