Split Camera.hdr out into a new component

[ecoskey]

Objective

• Simplify Camera initialization
• allow effects to require HDR

Solution

• Split out Camera.hdr into a marker Hdr component

Testing

• ran bloom_3d example

---

Showcase

// before
commands.spawn((
  Camera3d
  Camera {
    hdr: true
    ..Default::default()
  }
))

// after
commands.spawn((Camera3d, Hdr));

// other rendering components can require that the camera enables hdr!
// currently implemented for Bloom, AutoExposure, and Atmosphere.
#[require(Hdr)]
pub struct Bloom;

[github-actions]

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[JMS55]

I'm very much in favor of this change, but:
A) I think we should rename the component to something better
B) We should call out explicitly that this is internal render targets only, and not for display output, which is what people usually think of as HDR
C) We should really make this the default behavior

[Henauxg]

About the rename, now that it's a type and not a field, it could be something like HighDynamicRange instead of Hdr.
I'm not very aware about the "internal render targets only" details though, so maybe it needs an additional information in the name to carry that.

[Henauxg]

The blend_mode and transmission examples also seem like they need to be updated.

[IceSentry]

I'm very much in favor of this change, but:
A) I think we should rename the component to something better
B) We should call out explicitly that this is internal render targets only, and not for display output, which is what people usually think of as HDR
C) We should really make this the default behavior

I don't think A or C should happen in this PR. I'd prefer to keep this PR without too many behaviour changes. We can have a discussion about renaming it later.

For B, I think the current docs already do that?

[IceSentry]

I agree with the general direction of this PR. I haven't reviewed the changes yet though.

[hukasu]

I'm not very aware about the "internal render targets only" details though

from what i understand from being on the rendering channel for far too long is that each camera has a texture that they render to, and later it gets transferred to the swapchain texture, the camera's texture is Hdr but the swapchain's texture is not