feat: Add ConfigSynced event

Add an event for a case if a multi-device synced config value changed. Maybe the app needs to
refresh smth on such an event. For uniformity it is emitted on the source device too. The value is
omitted, otherwise it would be logged which might not be good for privacy.

deltachat-ffi/src/lib.rs

@@ -556,6 +556,7 @@ pub unsafe extern "C" fn dc_event_get_id(event: *mut dc_event_t) -> libc::c_int
         EventType::SecurejoinJoinerProgress { .. } => 2061,
         EventType::ConnectivityChanged => 2100,
         EventType::SelfavatarChanged => 2110,
+        EventType::ConfigSynced { .. } => 2111,
         EventType::WebxdcStatusUpdate { .. } => 2120,
         EventType::WebxdcInstanceDeleted { .. } => 2121,
     }
@@ -583,6 +584,7 @@ pub unsafe extern "C" fn dc_event_get_data1_int(event: *mut dc_event_t) -> libc:
         | EventType::Error(_)
         | EventType::ConnectivityChanged
         | EventType::SelfavatarChanged
+        | EventType::ConfigSynced { .. }
         | EventType::IncomingMsgBunch { .. }
         | EventType::ErrorSelfNotInGroup(_) => 0,
         EventType::MsgsChanged { chat_id, .. }
@@ -643,7 +645,8 @@ pub unsafe extern "C" fn dc_event_get_data2_int(event: *mut dc_event_t) -> libc:
         | EventType::ConnectivityChanged
         | EventType::WebxdcInstanceDeleted { .. }
         | EventType::IncomingMsgBunch { .. }
-        | EventType::SelfavatarChanged => 0,
+        | EventType::SelfavatarChanged
+        | EventType::ConfigSynced { .. } => 0,
         EventType::ChatModified(_) => 0,
         EventType::MsgsChanged { msg_id, .. }
         | EventType::ReactionsChanged { msg_id, .. }
@@ -722,6 +725,10 @@ pub unsafe extern "C" fn dc_event_get_data2_str(event: *mut dc_event_t) -> *mut
             .to_c_string()
             .unwrap_or_default()
             .into_raw(),
+        EventType::ConfigSynced { key } => {
+            let data2 = key.to_string().to_c_string().unwrap_or_default();
+            data2.into_raw()
+        }
     }
 }