Support XEP-0359: Unique and Stable Stanza IDs

[XEP-0359](https://xmpp.org/extensions/xep-0359.html)

This will help us identify which messages in a MUC were sent by us (https://github.com/profanity-im/profanity/issues/1201), and also will be useful later when we implement XEP-0313 MAM (https://github.com/profanity-im/profanity/issues/660) and XEP-0308 Last Message Correction (https://github.com/profanity-im/profanity/issues/805) too.