Bake Node for the Compositor

Been loving the compositor updates but it's easy to have filters taking 10+ seconds per compute. The node graph gets close to unusable very fast so it would be great if we could manually bake at certain points in the graph to act as a checkpoint.

Currently we can save an exr and import it as an image but it's a hassle and easy to forget to remove and inconvenient to update.

I expect better node update handling will be the long term solution for for now a bake node that simple saves the data internally like in Geo Nodes would be a great QOL update.