feat(label): address labels by name and add import and clone

label edit bug and label delete kind/feature failed with "invalid resource
number", and label create took its name as --name and required
--color. Like gh, label create takes the name as an argument and picks
a random color without -c; label edit and delete take names or IDs
(delete several at once, after a confirmation that names them), and
-c/-d/-n/-f are the gh short flags. Without a name on a terminal, label
create asks for the name, color and description.

label list shows ID NAME COLOR DESCRIPTION FLAGS with a colored swatch
and exclusive and archived labels flagged. Mutations report ✓ lines.
label import reads a label file or stdin (label create --file still
works), label clone copies another repository's labels, skipping those
that exist unless --force, and label export writes to stdout by default
or to -O/--output.

Signed-off-by: bircni <bircni@icloud.com>

internal/app/labelfile_test.go

@@ -86,5 +86,5 @@ func TestLabelImportAcceptsColorPrefixedRows(t *testing.T) {
 	require.Len(t, created, 2)
 	requirePayload(t, `{"name":"bug","color":"ee0701","description":"Something is not working"}`, strings.NewReader(created[0]))
 	requirePayload(t, `{"name":"enhancement","color":"84b6eb"}`, strings.NewReader(created[1]))
-	require.Equal(t, "1\tbug\t\t\n2\tenhancement\t\t\n", out.String())
+	require.Empty(t, out.String())
 }