[fix](regression) Fix agg_sync_mv data path

[shuke987]

What problem does this PR solve?

Issue Number: N/A

Related PR: #65133, #65336

Problem Summary:

The second streamLoad in nereids_syntax_p1/mv/aggregate/agg_sync_mv.groovy still uses the database and data-file path from before the case was moved into the aggregate directory.

The stale ../agg_mv_test.dat path does not exist. The stream load therefore returns no response, and the regression framework later reports the misleading Text must not be null or empty error while parsing it.

Align the second load with the working initial load by using database regression_test_nereids_syntax_p1_mv_aggregate and file agg_mv_test.dat.

Release note

None

Check List (For Author)

• Test

  • Regression test
  • Unit Test
  • Manual test (add detailed scripts or steps below)
  • No need to test or manual test. Explain why:
    • This is a refactor/code format and no logic has been changed.
    • Previous test can cover this change.
    • No code files have been changed.
    • Other reason: test-only path correction; git diff --check passes, the corrected data file exists, and the stale parent path does not.

• Behavior changed:

  • No.
  • Yes.

• Does this need documentation?

  • No.
  • Yes.

Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
• Confirm document
• Add branch pick label

[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?

[shuke987]

run buildall

[shuke987]

/review

[github-actions]

Reviewed PR #65538. I did not find a reportable issue.

Checkpoint conclusions:

• Goal/test proof: The patch fixes the second stream load in agg_sync_mv.groovy so it uses the p1 aggregate suite database and the aggregate data file path. Static framework inspection shows those are the correct targets.
• Scope/focusedness: The change is narrowly limited to the broken regression suite stream-load target.
• Concurrency/lifecycle/config/persistence/protocol: Not applicable; this is a test-only path change.
• Parallel paths: The p0 aggregate suite intentionally uses a different parent data-file/database layout; the p1 nested aggregate suite should use regression_test_nereids_syntax_p1_mv_aggregate and local agg_mv_test.dat.
• Test coverage/results: Existing .out coverage includes the final map_agg block, and the data has no conflicting duplicate key/value pairs after the second load and repeated self-inserts. I did not run the regression test because the review prompt forbids builds/test execution in this runner.
• User focus: No additional user-provided review focus.

[shuke987]

run buildall