Show visual feedback when BTTV and FFZ emotes are loaded (#1671)

Upon joining a channel or pressing F5, BTTV and FFZ emotes are
(re)loaded. This change adds visual feedback of the network requests and
their outcome, in the form of a system message in the associated
channel's chat window. 

Non-error messages are suppressed when joining a
channel (which automatically loads emotes).

src/widgets/splits/SplitHeader.cpp

@@ -765,8 +765,8 @@ void SplitHeader::reloadChannelEmotes()
 
     if (auto twitchChannel = dynamic_cast<TwitchChannel *>(channel.get()))
     {
-        twitchChannel->refreshFFZChannelEmotes();
-        twitchChannel->refreshBTTVChannelEmotes();
+        twitchChannel->refreshFFZChannelEmotes(true);
+        twitchChannel->refreshBTTVChannelEmotes(true);
     }
 }