Replace publicroomsapi with a combination of clientapi/roomserver/currentstateserver (#1174)

* Use content_value instead of membership

* Fix build

* Replace publicroomsapi with a combination of clientapi/roomserver/currentstateserver

- All public rooms paths are now handled by clientapi
- Requests to (un)publish rooms are sent to the roomserver via `PerformPublish`
  which are stored in a new `published_table.go`
- Requests for public rooms are handled in clientapi by:
    * Fetch all room IDs which are published using `QueryPublishedRooms` on the roomserver.
    * Apply pagination parameters to the slice.
    * Do a `QueryBulkStateContent` request to the currentstateserver to pull out
      required state event *content* (not entire events).
    * Aggregate and return the chunk.

Mostly but not fully implemented (DB queries on currentstateserver are missing)

* Fix pq query

* Make postgres work

* Make sqlite work

* Fix tests

* Unbreak pagination tests

* Linting

roomserver/api/query.go

@@ -215,3 +215,13 @@ type QueryRoomVersionForRoomRequest struct {
 type QueryRoomVersionForRoomResponse struct {
 	RoomVersion gomatrixserverlib.RoomVersion `json:"room_version"`
 }
+
+type QueryPublishedRoomsRequest struct {
+	// Optional. If specified, returns whether this room is published or not.
+	RoomID string
+}
+
+type QueryPublishedRoomsResponse struct {
+	// The list of published rooms.
+	RoomIDs []string
+}