Adds ViewportCoords Scene to examples/testbed/ui, Removes viewport_debug example

[kfc35]

Objective

• Closes Add a responsive coords scene to testbed_ui #21806

Solution

• Copies the setup contained in spawn_with_viewport_coords from viewport_debug into its own scene in the ui testbed. The testbed spawns a 1280 x 720 resolution window by default, so it looks the same.
• Removes the viewport_debug example (Although, tbh, I’m wondering if it’s actually worth keeping around since it might be useful for debugging for whatever reason. Second opinions welcome on the deletion of viewport_debug)

Testing

Ran cargo run --example testbed_ui and compared the new ViewportCoords scene via screenshot to the viewport_debug example (cargo run --example viewport_debug). They look the same.

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Showcase

To see the scene, checkout the branch and run cargo run --example testbed_ui. Hit the Spacebar 12x to see the new scene.

[kfc35]

The only differences between this function and spawn_with_viewport_coords from viewport_debug should be that:

• I removed the unused Palette color YELLOW (it’s only used in spawn_with_pixel_coords so the palette indices are shifted less by 1 for the children
• I added spawning the 2d Camera
• I added the DespawnOnExit component for the Camera and the parent node