Re-encrypts single-segment application messages when the network seqnum
has changed, to avoid encrypting messages with different seqnums in
network and transport. This operation is only required for unsegmented
messages, as segmented messages don't need to use the same seqnum in
network.
Reinstates the special adv data for friend messages to store the app key
index.
Stores friend queue packets unencrypted, removing any out-of-order
issues caused by seqnum allocation. Also moves as much of the metadata
storage as possible into the packet, allowing us to free up some bytes
of net_buf user data for friend packets.
