[v3] Add the Kptfile struct to render.

There are two approaches to read Kptfile. One is via templating which we can add comments to help users understand the Kptfile. The other is via go struct which is more accurate and less error-prone. Considering the reliability of the Kpt deprecation policies (the api schema is not expected to change and if it is changed it will be backward compatible. If not backward compatible, the deprecation has a year-long period)

Author: yuwenma

pkg/skaffold/render/renderer/renderer_test.go

@@ -16,13 +16,10 @@ limitations under the License.
 package renderer
 
 import (
-	"bytes"
-	"context"
 	"fmt"
 	"path/filepath"
 	"testing"
 
-	"github.com/GoogleContainerTools/skaffold/pkg/skaffold/graph"
 	"github.com/GoogleContainerTools/skaffold/pkg/skaffold/render/kptfile"
 	latestV2 "github.com/GoogleContainerTools/skaffold/pkg/skaffold/schema/latest/v2"
 	"github.com/GoogleContainerTools/skaffold/pkg/skaffold/util"
@@ -68,10 +65,6 @@ func TestRender_StoredInCache(t *testing.T) {
 			Write(filepath.Join(DefaultHydrationDir, kptfile.KptFileName), initKptfile).
 			Touch("empty.ignored").
 			Chdir()
+	}
 
-		var b bytes.Buffer
-		err := r.Render(context.Background(), &b, []graph.Artifact{{ImageName: "leeroy-web", Tag: "leeroy-web:v1"}})
-		t.CheckNoError(err)
-		t.CheckFileExistAndContent(filepath.Join(DefaultHydrationDir, dryFileName), []byte(labeledPodYaml))
-	})
-}
+}