Rename "container" to "image"

- Updated `wwctl upgrade` to handle updates
- Maintained `.Container` and `.ContainerName` in tstruct
- Added `ContainerName()` methods to node and profile objects
- Added `--container`, `-C` aliases to wwctl commands (`<node|profile> <add|set>`)
- Added `wwctl container` alias
- Added support for `container_exit.sh` if `image_exit.sh` is not found

Signed-off-by: Jonathon Anderson <janderson@ciq.com>

overlays/debug/internal/nodes.conf

@@ -28,7 +28,7 @@ nodes:
   node1:
     profiles:
     - default
-    container name: rockylinux-9
+    image name: rockylinux-9
     network devices:
       default:
         device: wwnet0