Worker to send temporary messages

[mahibi]

followup to #4422

Problems:

• When writing in chat A in offline mode and go to chat B, that messages in chat A are not sent automatically when device is online again.
• When writing in chat A in offline mode and then closing app, messages are not sent

Plan:
introduce a Worker to handle these cases.
It may be easier to switch from Dagger to Hilt before, as injecting a Dao into a worker with dagger is ugly. (@tobiasKaminsky offered help if it needs to be done with dagger)