Fix non-intuitive repository behavior

- The SaveBlob method now checks for duplicates.
- Moves handling of pending blobs to MasterIndex.
  -> also cleans up pending index entries when they are saved in the index
  -> when using SaveBlob no need to care about index any longer
- Always check for full index and save it when storing packs.
  -> removes the need of an index uploader
  -> also removes the verbose "uploaded intermediate index" messages
- The Flush method now also saves the index
- Fix race condition when checking and saving full/non-finalized indexes

internal/restorer/restorer_test.go

@@ -38,7 +38,7 @@ func saveFile(t testing.TB, repo restic.Repository, node File) restic.ID {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
-	id, err := repo.SaveBlob(ctx, restic.DataBlob, []byte(node.Data), restic.ID{})
+	id, _, err := repo.SaveBlob(ctx, restic.DataBlob, []byte(node.Data), restic.ID{}, false)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -118,11 +118,6 @@ func saveSnapshot(t testing.TB, repo restic.Repository, snapshot Snapshot) (*res
 		t.Fatal(err)
 	}
 
-	err = repo.SaveIndex(ctx)
-	if err != nil {
-		t.Fatal(err)
-	}
-
 	sn, err := restic.NewSnapshot([]string{"test"}, nil, "", time.Now())
 	if err != nil {
 		t.Fatal(err)