Worker to send temporary messages

[mahibi]

followup to https://github.com/nextcloud/talk-android/pull/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)

[mahibi]

from @SystemKeeper : iOS app has a maximum time to try to send an offline message (12h) https://github.com/nextcloud/talk-ios/blob/f74229bc7755941a838d6bb3a7778bac7522c17d/NextcloudTalk/NCRoomsManagerExtensions.swift#L385