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/app/wwctl/image/build/build_test.go

@@ -0,0 +1,20 @@
+package build
+
+import (
+	"testing"
+)
+
+// TestArgsImageBuild is a regression test for 215.
+func TestArgsImageBuild(t *testing.T) {
+	command := GetCommand()
+
+	err := command.Args(command, []string{})
+	if err != nil {
+		t.Errorf("no arguments to image build should succeed.")
+	}
+
+	err = command.Args(command, []string{"image1", "image2"})
+	if err != nil {
+		t.Errorf("multiple arguments to image build should succeed.")
+	}
+}