... to help align with original design intent
- dropped date breaks before msg groups
- show full date/timestamp in the msg header
- floating "Unpin" button on mouse hover
- no padding/spacing between messages
- some smaller code cleanups and dead code removals
Fixes#9396
- `chatType` added to `Constants` to group chat type related values
- `messageContentType` added to `Constants` to group message content type related
values
- `MessageStore` maintained per message list now
- added new `ChatContentView` component used to display chat/channel content
- components updated to display messages from the new backend
- `StatusChatToolBar` appropriately updated
- mute/unmute feature added to chat/channel list as well as to `StatusChatToolBar`