[Bugfix][Clickhouse] Fix clickhouse sink flush bug (#5448)

* [Bug][connector-cdc-mysql] mysql connections and memory of jvm increased abnormally (#5008)

* [bugfix][connector-cdc-mysql] reset the listener of binaryLogClient before fetch task start (#5008)

* [Bugfix][Clickhouse] fix when the checkpoint triggers flush, the connection is closed, causing subsequent data writing to fail

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Co-authored-by: dengjunjie <296442618@qq.com>

seatunnel-connectors-v2/connector-clickhouse/src/main/java/org/apache/seatunnel/connectors/seatunnel/clickhouse/sink/client/ClickhouseSinkWriter.java

@@ -90,7 +90,14 @@ public void write(SeaTunnelRow element) throws IOException {
 
     @Override
     public Optional<CKCommitInfo> prepareCommit() throws IOException {
-        flush();
+        for (ClickhouseBatchStatement batchStatement : statementMap.values()) {
+            JdbcBatchStatementExecutor statement = batchStatement.getJdbcBatchStatementExecutor();
+            IntHolder intHolder = batchStatement.getIntHolder();
+            if (intHolder.getValue() > 0) {
+                flush(statement);
+                intHolder.setValue(0);
+            }
+        }
         return Optional.empty();
     }