de-MSC-ifying space summaries (MSC2946) (#3134)

- This PR moves and refactors the
[code](https://github.com/matrix-org/dendrite/blob/main/setup/mscs/msc2946/msc2946.go)
for
[MSC2946](https://github.com/matrix-org/matrix-spec-proposals/pull/2946)
('Space Summaries') to integrate it into the rest of the codebase.
- Means space summaries are no longer hidden behind an MSC flag
- Solves #3096

Signed-off-by: Sam Wedgwood <sam@wedgwood.dev>

roomserver/internal/query/query.go

@@ -32,6 +32,7 @@ import (
 	"github.com/matrix-org/dendrite/syncapi/synctypes"
 
 	"github.com/matrix-org/dendrite/clientapi/auth/authtypes"
+	fsAPI "github.com/matrix-org/dendrite/federationapi/api"
 	"github.com/matrix-org/dendrite/internal/caching"
 	"github.com/matrix-org/dendrite/roomserver/acls"
 	"github.com/matrix-org/dendrite/roomserver/api"
@@ -47,6 +48,7 @@ type Queryer struct {
 	IsLocalServerName func(spec.ServerName) bool
 	ServerACLs        *acls.ServerACLs
 	Cfg               *config.Dendrite
+	FSAPI             fsAPI.RoomserverFederationAPI
 }
 
 func (r *Queryer) RestrictedRoomJoinInfo(ctx context.Context, roomID spec.RoomID, senderID spec.SenderID, localServerName spec.ServerName) (*gomatrixserverlib.RestrictedRoomJoinInfo, error) {