Add Client.emojis to get all emojis.

This removes the older get_all_emojis generator.

discord/state.py

@@ -160,6 +160,10 @@ class ConnectionState:
     def _remove_guild(self, guild):
         self._guilds.pop(guild.id, None)
 
+    @property
+    def emojis(self):
+        return list(self._emojis)
+
     @property
     def private_channels(self):
         return list(self._private_channels.values())