Allow attaching color image to be used as colormap on depth projection

[Wumpf]

We probably want to always automatically pick up color images on the same entity path as colormap for depth projection. But we need a way to specify this behavior - maybe we could simply look for a color image if the colormap is not set and use it then? Sounds a bit too implicit though, going back and forth from colormap to color image would then require resetting that component. So need to come up with some other way to model this

Example for what this can look like see https://github.com/rerun-io/rerun/issues/11562#issuecomment-3415250388

See also:

• https://github.com/rerun-io/rerun/issues/6897
• #10787

[teh-cmc]

Also:

• https://github.com/rerun-io/rerun/issues/2702

[Wumpf]

ah, that's the issue I was looking for actually. ... closing the old one as duplicate because this one has more info.