[fix](cloud) CloudUpgradeMgr inspect and abort failed conflict txns while waiting (#60830)

[deardeng]

pick from #60830

When CloudUpgradeMgr waits for unfinished transactions after registering

watershed txn ids, it now proactively inspects conflict transactions for

the target db/table set and logs sampled txn details for diagnosis.

If enable_abort_txn_by_checking_conflict_txn is enabled, the manager

invokes GlobalTransactionMgr.checkFailedTxns() and aborts failed txns to

reduce the chance of upgrade being blocked by stale/conflicting txns.

Abort failures are handled per txn and do not stop processing the rest.

This commit also adds tests:

• FE UT CloudUpgradeMgrTest to verify enabled/disabled behavior and

  continue-on-abort-error semantics.

• cloud multi_cluster docker regression case test_unfinished_txn_2pc.groovy

  to reproduce and validate long-running unfinished 2PC txn behavior.

(cherry picked from commit c6ea360)

What problem does this PR solve?

Issue Number: close #xxx

Related PR: #xxx

Problem Summary:

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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

• 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

[deardeng]

run buildall

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FE UT Coverage Report

Increment line coverage 75.00% (24/32) 🎉
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FE Regression Coverage Report

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