[test](be) Add DeletePredicate unit tests

[Gabriel39]

What problem does this PR solve?

Issue Number: close #xxx

Related PR: #xxx

Problem Summary: Add BE unit coverage for DeletePredicate execution, including row-id matches, empty deleted rows, out-of-range rows, empty blocks, unsupported execute_column_impl, and invalid child counts. Also fix boundary handling discovered while adding tests.

Release note

None

Check List (For Author)

• Test: Unit Test
  • Attempted build-support/clang-format.sh, but local macOS environment lacks Homebrew llvm@16.
  • Attempted ./run-be-ut.sh --run '--filter=DeletePredicateTest.*' -j 4, but local environment only has JDK 11 and the script requires JDK 17.
• Behavior changed: No
• Does this need documentation: No

What problem does this PR solve?

Issue Number: close #xxx

Related PR: #xxx

Problem Summary:

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

• 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]

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