Activating render region while using the CPU compositor produces corrupt
output for areas outside of the region when using the File Output node.
That's because the Full Frame compositor ignored nodes' render_border
flag, so the areas of interest of nodes that didn't consider render
border like the File Output were corrupt, producing uninitialized
outputs.
To fix this, we just consider the render_border flag when determining
output areas for output nodes in the Full Frame compositor.
Pull Request: https://projects.blender.org/blender/blender/pulls/128546
6ae3232eda