[Feature] Use a SortedList<> internally to store messages in MessagesListAdapter?

[rossica]

This could simplify the interface for adding new messages (instead of AddToEnd and AddToStart, there's just Add) and always ensure the proper order, if the backing store doesn't always return messages in the correct order.

I believe the type would look like SortedList<Wrapper>, and the callback for SortedList would call compare() on Wrapper.data, and equal() on Wrapper.data.
It would require, however, implementors of IMessage to implement compare() and equals() for that to work properly.