Use less memory

[emilk]

The Rerun Viewer currently use more memory than necessary. Luckily there are a bunch of low-hanging fruit. Like:

• Save .rrd from store instead of saving LogMsg:es. #1394
• Memory use: Use ref-counted buffers for images and meshes #1373

Images

DynamicImage

Don't cache DynamicImage in the ImageCache.
It is only used when zooming in on an image, and we could do that on the GPU instead

Don't store textures twice

We currently use 2x the VRAM for textures:

• Use less RAM: remove egui images from ImageStore #506

[emilk]

This is a badly named tracking issue. Let's just use the individual issues.