merge fdw_bugfix_6.0.0 into 6.0.0

postgres_fdw拓展适配XACT_EVENT_PRE_COMMIT和XACT_EVENT_PRE_PREPARE处理逻辑

Created-by: wofanzheng
Commit-by: wofanzheng
Merged-by: opengauss_bot
Description: 【标题】(请简要描述下实现的内容)
postgres_fdw拓展适配XACT_EVENT_PRE_COMMIT和XACT_EVENT_PRE_PREPARE处理逻辑

【实现内容】:
postgres_fdw拓展适配XACT_EVENT_PRE_COMMIT和XACT_EVENT_PRE_PREPARE处理逻辑

【根因分析】:
49059a76ef 新增两种事件类型XACT_EVENT_PRE_COMMIT和XACT_EVENT_PRE_PREPARE，但是postgres_fdw拓展没有做相应适配，导致pgfdw_xact_callback函数接受到事件XACT_EVENT_PRE_COMMIT之后直接结束了事务。导致外表没有更新成功。

【实现方案】:
pgfdw_xact_callback函数接受到事件XACT_EVENT_PRE_COMMIT之后，直接提交事务
【关联需求或issue】:
https://gitcode.com/opengauss/openGauss-server/issues/7202
【开发自验报告】:
1. 请附上自验结果(内容或者截图)
![image.png](https://raw.gitcode.com/user-images/assets/5089689/ebf2ddb6-8555-4ea8-82ac-507160b76e09/image.png 'image.png')
2. 是否可以添加fastcheck测试用例，如是，请补充fastcheck用例
不涉及
3. 是否涉及资料修改，如是，在docs仓库补充资料
不涉及
4. 是否考虑升级场景(系统表修改、日志持久化以及修改执行态数据格式)
不涉及
5. 是否考虑在线扩容等扩展场景
不涉及
6. 是否考虑异常场景/并发场景/前向兼容/性能场景
不涉及
7. 是否对其他模块产生影响
不涉及
【其他说明】:无

See merge request: opengauss/openGauss-server!7998

contrib/postgres_fdw/connection.cpp

@@ -822,9 +822,22 @@ static void pgfdw_xact_callback(XactEvent event, void *arg)
             elog(DEBUG3, "closing remote transaction on connection %p", entry->conn);
 
             switch (event) {
-                case XACT_EVENT_COMMIT:
+                case XACT_EVENT_PRE_COMMIT:
                     pgfdw_xact_callback_commit(entry);
                     break;
+                case XACT_EVENT_PRE_PREPARE:
+                	/*
+					 * We disallow any remote transactions, since it's not
+					 * very reasonable to hold them open until the prepared
+					 * transaction is committed.  For the moment, throw error
+					 * unconditionally; later we might allow read-only cases.
+					 * Note that the error will cause us to come right back
+					 * here with event == XACT_EVENT_ABORT, so we'll clean up
+					 * the connection state at that point.
+					 */
+                    elog(ERROR, "cannot PREPARE a transaction that has operated on postgres_fdw foreign tables");
+                    break;
+                case XACT_EVENT_COMMIT:
                 case XACT_EVENT_PREPARE:
                     /* Pre-commit should have closed the open transaction */
                     elog(ERROR, "missed cleaning up connection during pre-commit");