Fix computed.target_info not being updated after RenderTarget::None is modified

[kaio-matos]

Objective

• Keep camera.computed.target_info properly synced with RenderTarget::None changes.
• Fixes Camera.computed.target_info does not update when RenderTarget::None { size } is modified #23437

Solution

• Now NormalizedRenderTargetExt::is_changed returns true for NormalizedRenderTarget::None instead of false (not sure if this was the best solution, but I don't know any better to figure this out alone)

Testing

• Created a new testbed (not included in the PR since I've just used for local testing) using the code described in the issue and compared the output

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Showcase

Now camera.computed.target_info is synced with RenderTarget::None changes:

2026-03-31T00:40:17.175057Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(512, 512), scale_factor: 1.0 }), None { size: UVec2(512, 512) }
2026-03-31T00:40:17.283301Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(200, 200), scale_factor: 1.0 }), None { size: UVec2(200, 200) }
2026-03-31T00:40:17.869969Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(211, 211), scale_factor: 1.0 }), None { size: UVec2(211, 211) }
2026-03-31T00:40:17.905642Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(233, 233), scale_factor: 1.0 }), None { size: UVec2(233, 233) }
2026-03-31T00:40:17.912143Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(256, 256), scale_factor: 1.0 }), None { size: UVec2(256, 256) }
2026-03-31T00:40:17.925634Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(257, 257), scale_factor: 1.0 }), None { size: UVec2(257, 257) }
2026-03-31T00:40:17.943608Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(259, 259), scale_factor: 1.0 }), None { size: UVec2(259, 259) }
2026-03-31T00:40:17.959604Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(260, 260), scale_factor: 1.0 }), None { size: UVec2(260, 260) }
2026-03-31T00:40:17.973438Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(262, 262), scale_factor: 1.0 }), None { size: UVec2(262, 262) }
2026-03-31T00:40:17.990005Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(263, 263), scale_factor: 1.0 }), None { size: UVec2(263, 263) }
2026-03-31T00:40:18.004798Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(264, 264), scale_factor: 1.0 }), None { size: UVec2(264, 264) }
2026-03-31T00:40:18.016958Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(265, 265), scale_factor: 1.0 }), None { size: UVec2(265, 265) }
2026-03-31T00:40:18.029493Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(266, 266), scale_factor: 1.0 }), None { size: UVec2(266, 266) }
2026-03-31T00:40:18.042025Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(267, 267), scale_factor: 1.0 }), None { size: UVec2(267, 267) }
2026-03-31T00:40:18.054427Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(268, 268), scale_factor: 1.0 }), None { size: UVec2(268, 268) }