Implement and register Reflect (value) for CameraRenderGraph and CameraMainTextureUsages

[cart]

Objective

The new render graph labels do not (and cannot) implement normal Reflect, which breaks spawning scenes with cameras (including GLTF scenes). Likewise, the new CameraMainTextureUsages also does not (and cannot) implement normal Reflect because it uses wgpu::TextureUsages under the hood.

Fixes #11852

Solution

This implements minimal "reflect value" for CameraRenderGraph and CameraMainTextureUsages and registers the types, which satisfies our spawn logic.

Note that this does not fix scene serialization for these types, which will require more significant changes. We will especially need to think about how (and if) "interned labels" will fit into the scene system. For the purposes of 0.13, I think this is the best we can do. Given that this serialization issue is prevalent throughout Bevy atm, I'm ok with adding a couple more to the pile. When we roll out the new scene system, we will be forced to solve these on a case-by-case basis.

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Changelog

• Implement Reflect (value) for CameraMainTextureUsages and CameraRenderGraph, and register those types.

[alice-i-cecile]

Note that this does not fix scene serialization for these types, which will require more significant changes

So to be clear, this allows cameras to be spawned, but the exact values of these components are not properly preserved?

[cart]

So to be clear, this allows cameras to be spawned, but the exact values of these components are not properly preserved?

The GLTF loader constructs a Scene at runtime, which uses FromReflect to construct copies on spawn, which preserves the value because these components are "reflect values" / clone-able