Support upgrading warewulf.conf

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

internal/pkg/upgrade/slices.go

@@ -0,0 +1,17 @@
+package upgrade
+
+func indexOf[T comparable](slice []T, item T) int {
+	for i, v := range slice {
+		if v == item {
+			return i
+		}
+	}
+	return -1
+}
+
+func replaceSliceElement[T any](original []T, index int, replacement []T) []T {
+	if index < 0 || index >= len(original) {
+		return original
+	}
+	return append(original[:index], append(replacement, original[index+1:]...)...)
+}