Chat channel switching improvements (#4000)

* IC is default when joining;
switch to IC channel if IC channel becomes unavailable before trying OOC

* Allow channel cycling while the textbox is focused

* Fix focus channel keybinds not actually focusing

* Whitespess

* Fix duplicate radio

* Smol CycleChatChannel cleanup

* Revert style change

Content.Shared/Chat/ChatChannel.cs

@@ -61,5 +61,10 @@ namespace Content.Shared.Chat
         ///     Unspecified.
         /// </summary>
         Unspecified = 512,
+
+        /// <summary>
+        ///     Channels considered to be IC.
+        /// </summary>
+        IC = Local | Radio | Dead | Emotes | Damage | Visual,
     }
 }