Currently we color-map tensors and depth-images on the CPU. This has many downsides:

• It is slower
• It requires complex caching on the CPU
• It blocks Use less RAM: remove egui images from ImageStore #506

Instead, let's improve the re_renderer::TexturedRect API to handle:

• Color map selector enum
• A range for the color map
• Gamma
• Color maps for all 2D tensors in the image view
• Color maps for all tensors in the tensor view

Misc TODO

• Remove the extra enum Colormap that we have
• Support texture filtering