Don't limit "state" (#2849)

This is apparently some incorrect behaviour that we built as a result of
a spec bug (matrix-org/matrix-spec#1314) where we were applying a filter
to the `"state"` section of the `/sync` response incorrectly. The client
then has no way to know that the state was limited.

This PR removes the state limiting, which probably also helps #2842.

syncapi/storage/sqlite3/current_room_state_table.go

@@ -277,7 +277,8 @@ func (s *currentRoomStateStatements) SelectCurrentState(
 		},
 		stateFilter.Senders, stateFilter.NotSenders,
 		stateFilter.Types, stateFilter.NotTypes,
-		excludeEventIDs, stateFilter.ContainsURL, stateFilter.Limit, FilterOrderNone,
+		excludeEventIDs, stateFilter.ContainsURL, 0,
+		FilterOrderNone,
 	)
 	if err != nil {
 		return nil, fmt.Errorf("s.prepareWithFilters: %w", err)

syncapi/storage/sqlite3/filtering.go

@@ -84,8 +84,10 @@ func prepareWithFilters(
 	case FilterOrderDesc:
 		query += " ORDER BY id DESC"
 	}
-	query += fmt.Sprintf(" LIMIT $%d", offset+1)
-	params = append(params, limit)
+	if limit > 0 {
+		query += fmt.Sprintf(" LIMIT $%d", offset+1)
+		params = append(params, limit)
+	}
 
 	var stmt *sql.Stmt
 	var err error

syncapi/storage/sqlite3/output_room_events_table.go

@@ -200,7 +200,7 @@ func (s *outputRoomEventsStatements) SelectStateInRange(
 			s.db, txn, stmtSQL, inputParams,
 			stateFilter.Senders, stateFilter.NotSenders,
 			stateFilter.Types, stateFilter.NotTypes,
-			nil, stateFilter.ContainsURL, stateFilter.Limit, FilterOrderAsc,
+			nil, stateFilter.ContainsURL, 0, FilterOrderAsc,
 		)
 	} else {
 		stmt, params, err = prepareWithFilters(