branch-4.0: [fix](regression) Wait row count before partition stats check

[yujun777]

What problem does this PR solve?

The partition row count regression asserts selected partition stats from BE-reported row counts. In Cloud, this row count can be stale immediately after insert, so wait until SHOW DATA reports the expected table row count before analyze and explain.

Check List

• Test: git diff --check
• Behavior changed: No
• Does this need documentation: No

[hello-stephen]

Thank you for your contribution to Apache Doris.
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Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?

[yujun777]

run buildall