CameraBundle clarifications

## How can Bevy's documentation be improved?

I went through all the components and fields of the camera bundles, and had some unanswered questions as a rendering noob.

- Is `Camera::msaa_writeback` redundant with `CameraOutputMode::Skip`, and also with `CameraOutputMode::Write` using `LoadOp::Load` (on top of a camera that uses `LoadOp::Clear`)?
- `Camera -> ClearColorConfig`
- Is this redundant with `CameraOutputMode` using `LoadOp Clear/Load`?
- What if the camera has `CameraOutputMode::Skip`?
- How does this interact with `msaa_writeback`?
- `Camera3D -> Camera3dDepthOp`
- How does this differ from/relate to the `Camera's` `CameraOutputMode`?
- Is the depth in `Camera3dDepthLoadOp::Load` normalized or in world units?