Add AuronQueryTest: compare results with vanilla Spark and check native operators

[yew1eb]

Is your feature request related to a problem? Please describe.

• Manually writing expected results is error-prone, hard to maintain, and often breaks across spark versions duto to behavioral differences.
• Many existing tests never verify the physical plan; in practice, a lot of cases silently fallback to vanilla spark instead of executing with native operators.

Describe the solution you'd like

• Add AuronQueryTest extending org.apache.spark.sql.QueryTest
• Provide helpers to:
  • Run a query once with native disabled to collect the baseline(vanilla spark), then run with native enabled ans assert results match vanilla spark.
  • Optionally enforce that the physical plan contains only native operators (ignoring stage/adapter nodes), failing fast otherwise.

Describe alternatives you've considered

Additional context

[yew1eb]

cc @merrily01 @richox