refactor(scrub): replace umoci logic in scrub implementation (#1845)

- implement scrub also for S3 storage by replacing umoci
- change scrub implementation for ImageIndex
- take the `Subject` into consideration when running scrub
- remove test code relying on the umoci library. Since we started
relying on images in test/data, and we create our own images using
go code we can obtain digests by other means. (cherry picked from commit 489d4e2d23c1b4e48799283f8281024bbef6123f)

Signed-off-by: Andrei Aaron <aaaron@luxoft.com>
Signed-off-by: Andreea-Lupu <andreealupu1470@yahoo.com>

pkg/api/controller_test.go

@@ -4350,7 +4350,7 @@ func TestInvalidCases(t *testing.T) {
 			panic(err)
 		}
 
-		digest := test.GetTestBlobDigest("zot-cve-test", "config").String()
+		digest := godigest.FromString("dummy").String()
 		name := "zot-c-test"
 
 		client := resty.New()
@@ -4449,7 +4449,8 @@ func TestCrossRepoMount(t *testing.T) {
 		ctlr.Config.Storage.RemoteCache = false
 		ctlr.Config.Storage.Dedupe = false
 
-		err := test.WriteImageToFileSystem(CreateDefaultImage(), "zot-cve-test", "test", storage.StoreController{
+		image := CreateDefaultImage()
+		err := test.WriteImageToFileSystem(image, "zot-cve-test", "test", storage.StoreController{
 			DefaultStore: test.GetDefaultImageStore(dir, ctlr.Log),
 		})
 		So(err, ShouldBeNil)
@@ -4459,8 +4460,7 @@ func TestCrossRepoMount(t *testing.T) {
 
 		params := make(map[string]string)
 
-		var manifestDigest godigest.Digest
-		manifestDigest, _, _ = test.GetOciLayoutDigests(path.Join(dir, "zot-cve-test"))
+		manifestDigest := image.ManifestDescriptor.Digest
 
 		dgst := manifestDigest
 		name := "zot-cve-test"
@@ -4487,7 +4487,7 @@ func TestCrossRepoMount(t *testing.T) {
 			baseURL, constants.RoutePrefix, constants.Blobs, constants.Uploads))
 
 		incorrectParams := make(map[string]string)
-		incorrectParams["mount"] = test.GetTestBlobDigest("zot-cve-test", "manifest").String()
+		incorrectParams["mount"] = godigest.FromString("dummy").String()
 		incorrectParams["from"] = "zot-x-test"
 
 		postResponse, err = client.R().