fs / archiver: convert to handle based interface

The actual implementation still relies on file paths, but with the
abstraction layer in place, an FS implementation can ensure atomic file
accesses in the future.

internal/fs/node_windows_test.go

@@ -222,11 +222,11 @@ func restoreAndGetNode(t *testing.T, tempDir string, testNode *restic.Node, warn
 	test.OK(t, errors.Wrapf(err, "Failed to restore metadata for: %s", testPath))
 
 	fs := &Local{}
-	fi, err := fs.Lstat(testPath)
-	test.OK(t, errors.Wrapf(err, "Could not Lstat for path: %s", testPath))
-
-	nodeFromFileInfo, err := fs.NodeFromFileInfo(testPath, fi, false)
+	meta, err := fs.OpenFile(testPath, O_NOFOLLOW, true)
+	test.OK(t, err)
+	nodeFromFileInfo, err := meta.ToNode(false)
 	test.OK(t, errors.Wrapf(err, "Could not get NodeFromFileInfo for path: %s", testPath))
+	test.OK(t, meta.Close())
 
 	return testPath, nodeFromFileInfo
 }