[fix](mtmv)Compatible old mtmv metadata (apache#26193)

make sure user can upgrade from v2.0 to master

fe/fe-core/src/main/java/org/apache/doris/catalog/MTMV.java

@@ -0,0 +1,32 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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 org.apache.doris.catalog;
+
+import org.apache.doris.common.io.Text;
+
+import java.io.DataInput;
+import java.io.IOException;
+
+public class MTMV extends OlapTable {
+
+    @Override
+    public void readFields(DataInput in) throws IOException {
+        super.readFields(in);
+        Text.readString(in);
+    }
+}

fe/fe-core/src/main/java/org/apache/doris/catalog/Table.java

@@ -363,6 +363,8 @@ public static Table read(DataInput in) throws IOException {
         TableType type = TableType.valueOf(Text.readString(in));
         if (type == TableType.OLAP) {
             table = new OlapTable();
+        } else if (type == TableType.MATERIALIZED_VIEW) {
+            table = new MTMV();
         } else if (type == TableType.ODBC) {
             table = new OdbcTable();
         } else if (type == TableType.MYSQL) {