[IOTDB-6357] Fix Bugs in AlignByDeviceOrderByLimitOffsetTest

[chihyu0917]

Description

I report the problem in the issue #16593

Solutions

1. Walk the subtree instead instead of pinning to indices. Added helper containsNodeType(PlanNode, Class<?>) that recursively checks for a given node class.
2. Accept either DeviceViewNode or SingleDeviceViewNode. Assertions now allow both legitimate alternatives.
3. Reused the helper across all four tests, so they tolerate harmless structural differences and stay reliable under random seeds shuffling.

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This PR has:

• been self-reviewed.
  • concurrent read
  • concurrent write
  • concurrent read and write
• added documentation for new or modified features or behaviors.
• added Javadocs for most classes and all non-trivial methods.
• added or updated version, license, or notice information
• added comments explaining the "why" and the intent of the code wherever would not be obvious
  for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold
  for code coverage.
• added integration tests.
• been tested in a test IoTDB cluster.

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Key changed/added classes (or packages if there are too many classes) in this PR

[github-actions]

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