Remove references to schema1 pacakge from proxy package

schema1 package was deprecated a while ago so we are removing
any references to it from the proxy package in preparation to
removing it from the codebase altogether.

Signed-off-by: Milos Gajdos <milosthegajdos@gmail.com>

testutil/push.go

@@ -0,0 +1,36 @@
+package testutil
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	"github.com/distribution/distribution/v3"
+	"github.com/opencontainers/go-digest"
+)
+
+// PushBlob pushes a blob with the given digest to the given repository.
+func PushBlob(ctx context.Context, repository distribution.Repository, blobReader io.ReadSeeker, dgst digest.Digest) error {
+	blobs := repository.Blobs(ctx)
+
+	wr, err := blobs.Create(ctx)
+	if err != nil {
+		return fmt.Errorf("error creating layer upload: %v", err)
+	}
+
+	// Use the resumes, as well!
+	wr, err = blobs.Resume(ctx, wr.ID())
+	if err != nil {
+		return fmt.Errorf("error resuming layer upload: %v", err)
+	}
+
+	if _, err := io.Copy(wr, blobReader); err != nil {
+		return fmt.Errorf("unexpected error uploading: %v", err)
+	}
+
+	if _, err := wr.Commit(ctx, distribution.Descriptor{Digest: dgst}); err != nil {
+		return fmt.Errorf("unexpected error finishing upload: %v", err)
+	}
+
+	return nil
+}