Remove PerformError (#3066)

This removes `PerformError`, which was needed when we still had
polylith.

This removes quite a bunch of
```go
if err != nil {
	return err
}
if err := res.Error; err != nil {
	return err.JSONResponse()
}
```

Hopefully can be read commit by commit. [skip ci]

roomserver/internal/perform/perform_publish.go

@@ -25,16 +25,10 @@ type Publisher struct {
 	DB storage.Database
 }
 
+// PerformPublish publishes or unpublishes a room from the room directory. Returns a database error, if any.
 func (r *Publisher) PerformPublish(
 	ctx context.Context,
 	req *api.PerformPublishRequest,
-	res *api.PerformPublishResponse,
 ) error {
-	err := r.DB.PublishRoom(ctx, req.RoomID, req.AppserviceID, req.NetworkID, req.Visibility == "public")
-	if err != nil {
-		res.Error = &api.PerformError{
-			Msg: err.Error(),
-		}
-	}
-	return nil
+	return r.DB.PublishRoom(ctx, req.RoomID, req.AppserviceID, req.NetworkID, req.Visibility == "public")
 }