[HUDI-2432] Adding restore.requested instant and restore plan for restore action (#4605)

- This adds a restore plan and serializes it to restore.requested meta file in timeline. This also means that we are introducing schedule and execution phases for restore which was not present before.

hudi-common/src/main/avro/HoodieRestorePlan.avsc

@@ -0,0 +1,37 @@
+/*
+ * 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.
+ */
+{
+   "namespace":"org.apache.hudi.avro.model",
+   "type":"record",
+   "name":"HoodieRestorePlan",
+   "fields":[
+    {
+           "name": "instantsToRollback",
+           "default": [],
+           "type": {
+             "type": "array",
+             "default": null,
+             "items": "HoodieInstantInfo"
+           }
+    },
+    {
+           "name":"version",
+           "type":["int", "null"],
+           "default": 1
+    }]
+}