- Rework the MAM Preference dialog
- Move MAM Preference dialog into a new gtk module
- Refactor all MAM code into own module
- Refactor the MAM code itself so we can easier test it in the future
- Add a misc module for smaller XEPs and move EME, Last Message Correction
Delay, OOB into it
- Add dedicated module for XEP-0082 Time Profiles
Fixes#8810
Also remove mam_start_date migration.
mam_start_date didnt exist in Gajim 0.16.x and it doesnt hurt
if people who used the dev version download some extra messages.
Our deduplication algorithm should take care of it.