feat: Add StreamRecordTimestampInserter operator

[ggjh-159]

Issue: gluten#12426

Summary

Adds a new stateful operator StreamRecordTimestampInserter to velox/experimental/stateful/, the native counterpart of Flink's org.apache.flink.table.runtime.operators.sink.StreamRecordTimestampInserter.

Unlike the row-based Flink original (which reads the rowtime column row-by-row and stamps each StreamRecord), this operator works in columnar batches:

• Reads the rowtime column of each input batch
• Computes the batch's max timestamp (in epoch millis)
• Emits the original RowVector wrapped in a StreamRecord carrying that timestamp

No watermark generation, no batch splitting — RowVector passes through end-to-end. Operator logic and plan node live entirely in C++.

Changes

• New velox/experimental/stateful/StreamRecordTimestampInserter.{h,cpp} — operator implementation.
• Modified velox/experimental/stateful/StatefulPlanNode.{h,cpp} — adds StreamRecordTimestampInserterNode PlanNode with project + rowtimeFieldIndex fields, registers serde ("StreamRecordTimestampInserterNode").
• Modified velox/experimental/stateful/StatefulPlanner.{h,cpp} — adds dispatch + transformStreamRecordTimestampInserterOperator.
• Modified velox/experimental/stateful/CMakeLists.txt — adds StreamRecordTimestampInserter.cpp to velox_stateful_exec.
• New velox/experimental/stateful/tests/StreamRecordTimestampInserterTest.cpp + CMakeLists entry — unit tests.

Test plan

• UTs.
• End-to-end nexmark q0 validation.

[KevinyhZou]

The result of watermark::getTimestampVector(...) should be SimpleVector<int64_t> ? and this can be seen from WatermarkGenerator and WatermarkAssigner

[ggjh-159]

In Flink file org/apache/flink/table/runtime/operators/sink/StreamRecordTimestampInserter.java

    @Override
    public void processElement(StreamRecord<RowData> element) throws Exception {
        final RowData rowData = element.getValue();
        // timestamp might be TIMESTAMP or TIMESTAMP_LTZ
        final long rowtime = rowData.getTimestamp(rowtimeIndex, precision).getMillisecond();
        element.setTimestamp(rowtime);
        output.collect(element);
    }

The type of the column vector at index rowtimeIndex should be Timestamp.

[KevinyhZou]

if input.size == 0, then maxTs = std::numeric_limits<int64_t>::min(), StreamRecord.hasTImestamp should be false

[KevinyhZou]

LGTM

[lgbo-ustc]

format the code

[ggjh-159]

format the code

@lgbo-ustc cc