Update ChatDocumentHandler so RoomManger is no longer required for saving text

Update `ChatDocumentHandler` so `RoomManger` is no longer required for saving the text in the chatbar between room switches. This is achieved by allowing `ChatDocumentHandler` to get the correct `ChatBarChache` itself rather than having to have it passed from `ChatBar.qml`. This avoids any race conditions.

src/libneochat/neochatroom.h

@@ -12,6 +12,7 @@
 
 #include <QCoroTask>
 
+#include "enums/chatbartype.h"
 #include "enums/messagetype.h"
 #include "enums/pushrule.h"
 #include "events/pollevent.h"
@@ -484,6 +485,8 @@ public:
 
     ChatBarCache *threadCache() const;
 
+    ChatBarCache *cacheForType(ChatBarType::Type type) const;
+
     /**
      * @brief Reply to the last message sent in the timeline.
      *