Color chat senders by GUID and drop the who-search option

The engine name-queries a chat sender before the CHAT_MSG event fires,
so GetPlayerInfoByGUID(GetCurrentChatGUID()) resolves every player
sender, including strangers in world channels. Other names in the text
still fall back to C_PlayerCache.GetPlayerInfoByName and libunitscan.

This makes the silent /who lookup for unknown classes obsolete; remove
it along with its FriendsFrame_OnEvent wrapper, config default, GUI
entry and translations.

env/translations_frFR.lua

@@ -872,7 +872,6 @@ pfUI_translation["frFR"] = {
   ["Website"] = "Site web",
   ["Welcome to |cff33ffccpf|cffffffffUI|r!\n\nI'm the first run wizard that will guide you through some basic configuration. If you're lazy, feel free to hit the \"Defaults\" button. If you wish to run this dialog again, go to the settings and hit the \"Reset Firstrun\" button.\n\nVisit |cff33ffcc%s|r to check for the latest version."] = "Bienvenue sur l'assistant d'installation de l'interface |cff33ffccpf|cffffffffUI|r!\n\nNous allons effectuer quelques configurations de base. Si vous n'avez pas la patience, cliquer sur le bouton \"Paramètres par défaut\". Si vous souhaitez relancer cette fenêtre de dialogue, allez dans les options et cliquez sur le bouton\"Réinitialiser l'assistant d'installation\" .\n\nAllez sur |cff33ffcc%s|r pour télécharger la dernière version.",
   ["Whitelist"] = "List blanche",
-  ["Who Search Unknown Classes (|cffffaaaaExperimental|r)"] = nil,
   ["Width"] = "Largeur",
   ["Wobble Zoom"] = "Zoom oscillant",
   ["Won"] = "A gagné",