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>

internal/pkg/node/methods.go

@@ -311,6 +311,16 @@ func (node *Profile) Id() string {
 	return node.id
 }
 
+// ContainerName returns the value of the ImageName field for backwards-compatibility.
+func (node *Node) ContainerName() string {
+	return node.ImageName
+}
+
+// ContainerName returns the value of the ImageName field for backwards-compatibility.
+func (profile *Profile) ContainerName() string {
+	return profile.ImageName
+}
+
 /*
 Returns if the node is a valid in the database
 */