Remove gmsl.HeaderedEvent (#3068)

Replaced with types.HeaderedEvent _for now_. In reality we want to move
them all to gmsl.Event and only use HeaderedEvent when we _need_ to
bundle the version/event ID with the event (seriailsation boundaries,
and even then only when we don't have the room version).

Requires https://github.com/matrix-org/gomatrixserverlib/pull/373

roomserver/storage/tables/interface.go

@@ -95,7 +95,7 @@ type StateSnapshot interface {
 
 	BulkSelectMembershipForHistoryVisibility(
 		ctx context.Context, txn *sql.Tx, userNID types.EventStateKeyNID, roomInfo *types.RoomInfo, eventIDs ...string,
-	) (map[string]*gomatrixserverlib.HeaderedEvent, error)
+	) (map[string]*types.HeaderedEvent, error)
 }
 
 type StateBlock interface {
@@ -196,7 +196,7 @@ type StrippedEvent struct {
 // ExtractContentValue from the given state event. For example, given an m.room.name event with:
 // content: { name: "Foo" }
 // this returns "Foo".
-func ExtractContentValue(ev *gomatrixserverlib.HeaderedEvent) string {
+func ExtractContentValue(ev *types.HeaderedEvent) string {
 	content := ev.Content()
 	key := ""
 	switch ev.Type() {