Update disappearing message TTL on swarm when a message is seen

[sakurayz]

When using the recovery phrase to recover the account, the deleted messages and groups should not be recovered. For safety, because the message has been deleted

[KeeJef]

When a Disappearing message is first seen, the client should lower the TTL of the message on the storage server + swarm to whatever the disappearing message timer is sent to. Or we could allow the sender to set the TTL of the message to whatever the disappearing message timer is. Both have advantages and disadvantages