[fix](regression) wait row count for partition_key_minmax

[shuke987]

Proposed changes

partition_key_minmax checks partition-pruned memo-plan statistics. In Cloud P0, this case can run the EXPLAIN before the physical index row count has finished reporting after insert/analyze. When that happens, the planner's selected-partition row count can be 0, so the existing ndv/count assertions fail even though the partition-key min/max is already correct.

This patch keeps the existing EXPLAIN assertions and adds a bounded wait for the base index strict row count via show index stats <table> <index> before running each memo-plan check.

Testing

• git diff --check

No local regression environment was allocated in this session, so the targeted regression case was not run locally.

[hello-stephen]

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[shuke987]

run buildall

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