Add an Overlay type with helper methods

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

internal/pkg/configure/hostfile.go

@@ -14,8 +14,8 @@ import (
 Creates '/etc/hosts' from the host template.
 */
 func Hostfile() (err error) {
-	overlaySourceDir, _ := overlay.GetOverlay("host")
-	hostTemplate := path.Join(overlaySourceDir, "/etc/hosts.ww")
+	overlay_ := overlay.GetOverlay("host")
+	hostTemplate := path.Join(overlay_.Rootfs(), "/etc/hosts.ww")
 	if !(util.IsFile(hostTemplate)) {
 		return fmt.Errorf("'the overlay template '/etc/hosts.ww' does not exists in 'host' overlay")
 	}