[fix](mtmv) fix mtmv task nereids cost too much time (#37589)

cause: when mtmv task need refresh multi partition, will be split into
multiple `insert overwrite` tasks,they use same `ConnectContext` and
`StatementContext`,nereids time is calculated based on StatementContext,
so multiple tasks will accumulate time

fix: each `insert overwrite` tasks use unique `StatementContext`

fe/fe-core/src/main/java/org/apache/doris/job/extensions/mtmv/MTMVTask.java

@@ -41,6 +41,7 @@
 import org.apache.doris.mtmv.MTMVRefreshPartitionSnapshot;
 import org.apache.doris.mtmv.MTMVRelation;
 import org.apache.doris.mtmv.MTMVUtil;
+import org.apache.doris.nereids.StatementContext;
 import org.apache.doris.nereids.glue.LogicalPlanAdapter;
 import org.apache.doris.nereids.trees.plans.commands.UpdateMvByPartitionCommand;
 import org.apache.doris.nereids.trees.plans.commands.info.TableNameInfo;
@@ -222,6 +223,9 @@ public void run() throws JobException {
     private void exec(ConnectContext ctx, Set<String> refreshPartitionNames,
             Map<TableIf, String> tableWithPartKey)
             throws Exception {
+        Objects.requireNonNull(ctx, "ctx should not be null");
+        StatementContext statementContext = new StatementContext();
+        ctx.setStatementContext(statementContext);
         TUniqueId queryId = generateQueryId();
         lastQueryId = DebugUtil.printId(queryId);
         // if SELF_MANAGE mv, only have default partition,  will not have partitionItem, so we give empty set