MSC2836 threading: part 2 (#1596)

* Update GMSL

* Add MSC2836EventRelationships to fedsender

* Call MSC2836EventRelationships in reqCtx

* auth remote servers

* Extract room ID and servers from previous events; refactor a bit

* initial cut of federated threading

* Use the right client/fed struct in the response

* Add QueryAuthChain for use with MSC2836

* Add auth chain to federated response

* Fix pointers

* under CI: more logging and enable mscs, nil fix

* Handle direction: up

* Actually send message events to the roomserver..

* Add children and children_hash to unsigned, with tests

* Add logic for exploring threads and tracking children; missing storage functions

* Implement storage functions for children

* Add fetchUnknownEvent

* Do federated hits for include_children if we have unexplored children

* Use /ev_rel rather than /event as the former includes child metadata

* Remove cross-room threading impl

* Enable MSC2836 in the p2p demo

* Namespace mscs db

* Enable msc2836 for ygg

Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>

roomserver/api/query.go

@@ -275,6 +275,14 @@ type QueryPublishedRoomsResponse struct {
 	RoomIDs []string
 }
 
+type QueryAuthChainRequest struct {
+	EventIDs []string
+}
+
+type QueryAuthChainResponse struct {
+	AuthChain []*gomatrixserverlib.HeaderedEvent
+}
+
 type QuerySharedUsersRequest struct {
 	UserID         string
 	ExcludeRoomIDs []string