Avoid jump in size when switching images in the UV editor

Right now, when you change the displayed image in the UV editor, the UV canvas changes size based on the resolution of the image. This makes no sense given that the UV space should be the focus in the UV editor. I propose for the canvas to remain fixed in its current size, and for the image itself to be scaled to fit in. For non uniform images, the largest axis could be used as the fixed part. (See Gifs embeded below)

I also propose to get rid of the Render Result and Viewer Node options for the UV editor specifically. Not only they don't display the UV map, they make the UI of the header jump by hiding options. Render Result and Viewer node should be visible on the Image Editor only, where they are used. On top of that, if your Render Display mode is set up as Image Editor (the one where the UI remains the same except for one editor) the UV editor might be used to display the Render, instead of switching to an image editor, so that should take care of this problem as well.

All of these are remnants of the Image editor and the UV editor being the same editor originally, which at first I was against splitting, but improvements like this should help justify the change and make things better

Current:

Proposed: