Main changes:
- Extend saved addresses DB with sync info: sync timestamp, update timestamp
and soft removed flag
- Create custom protobuf message payload to sync saved addresses
- Cleanup saved addresses on each start of messenger, by deleting
soft removed older entries
- Sync all saved addresses on Messenger.SyncDevices calls
- Sync particular changes to saved addresses
- Add SavedAddressManager instance to messenger
- Note, can't find a clean way to pass the SavedAddressManager to the
messenger, so we create another one
- Add tests for sync and new DB API
Closes: #7229
Stefan