Upgrade hcl to v2

Signed-off-by: Patrick Van Stee <patrick@vanstee.me>

vendor/github.com/zclconf/go-cty/cty/set/iterator.go

@@ -0,0 +1,15 @@
+package set
+
+type Iterator struct {
+	vals []interface{}
+	idx  int
+}
+
+func (it *Iterator) Value() interface{} {
+	return it.vals[it.idx]
+}
+
+func (it *Iterator) Next() bool {
+	it.idx++
+	return it.idx < len(it.vals)
+}