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/types/headered_event.go

@@ -0,0 +1,47 @@
+// Copyright 2023 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package types
+
+import (
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+// HeaderedEvent is an Event which serialises to the headered form, which includes
+// _room_version and _event_id fields.
+type HeaderedEvent struct {
+	*gomatrixserverlib.Event
+	Visibility gomatrixserverlib.HistoryVisibility
+}
+
+func (h *HeaderedEvent) MarshalJSON() ([]byte, error) {
+	return h.Event.ToHeaderedJSON()
+}
+
+func (j *HeaderedEvent) UnmarshalJSON(data []byte) error {
+	ev, err := gomatrixserverlib.NewEventFromHeaderedJSON(data, false)
+	if err != nil {
+		return err
+	}
+	j.Event = ev
+	return nil
+}
+
+func NewEventJSONsFromHeaderedEvents(hes []*HeaderedEvent) gomatrixserverlib.EventJSONs {
+	result := make(gomatrixserverlib.EventJSONs, len(hes))
+	for i := range hes {
+		result[i] = hes[i].JSON()
+	}
+	return result
+}