fix: merge into split

[dantengsky]

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Summary

for merge-into stmt with both matched and not-matched branch, right join is used,
after got the joined result-set, a column of the result-set is chosen as the "split" column,
i.e. for rows of the split column, those are nulls are recognized as no-matched, and others as matched.

before this PR, an arbitrary column of target table is picked as the "split" column, which is unsafe, since
the "arbitrary column" may have NULL values originally, which may lead to incorrectly treat a matched row
as unmatched, and unexpected result (data duplication).

in this PR, we use row_id column to split the result-set into matched and not-matched parts

• Fixes bug: MERGE INTO duplicates rows unexpectedly #15643

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

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This change is 

[xudong963]

Error: SelfError("sqllogictest failed")
Completed MySQL test for file: tests/sqllogictests/suites/base/09_fuse_engine/09_0036_merge_into_without_distributed_enable.test ✅ (90.038121213s)
Test finished, fail fast enabled, 1 out of 6480 records failed to run
0: statement failed: mysql client error: Server error: `ERROR HY000 (1105): TableAlreadyLocked. Code: 2015, Text = table is locked by other session, please retry later.'
[SQL] alter table tbl_01_0007 recluster final where a != 4
at tests/sqllogictests/suites/base/01_system/01_0007_system_clustering_history.test:16