feat(noitu): make /noitu the group game and add /noitutop

/noitu now posts the group play card that /noitupvp used to, and the solo
game against the bot moves to /noitubot. In a private chat /noitu points
the user to a group, or to /noitubot.

/noitutop ranks a group's players across all of its cards by wins, best
game and games played.

A one-time startup migration moves /stats history to the new names in
order: noitu to noitubot first, then noitupvp to noitu.

cmd/server/command_menu_test.go

@@ -74,7 +74,8 @@ func TestCommandDiscovery_AllPublicCommandsHaveSafeMetadata(t *testing.T) {
 		"monkeyd_crawl":        "<url> [font_size]",
 		"monkeyd_tags":         "<url>",
 		"noitu":                "",
-		"noitupvp":             "",
+		"noitubot":             "",
+		"noitutop":             "",
 		"random":               "<option,...>",
 		"addsticker":           "[emoji...]",
 		"alias":                "<name>",