Creating a new scene should never use the same name as an existing scene

[jleibs]

When creating a "camera" scene in the colmap it confusingly ends up named "image".

The scene is layed out as:

And the initial scene is good:

However, if I add a third scene for the camera:

Then we end up with a second scene named image:

I think this scene should be named camera because that's what's in the scene: a camera that contains an image but I'd settle for image2 to at least help me track which is which.

[jleibs]

In general I'm trying to come up with a scenario where I don't want the last element of the space root to be the default name.

[Wumpf]

This is trivial to fix, just remove the first branch here https://github.com/rerun-io/rerun/blob/main/crates/re_viewer/src/ui/space_view.rs#L65
I'm not sure that's always what we want though. In your example is seems reasonable enough hover