[SPARK-56563][SQL][TESTS] Merge SparkPlanTest into QueryTest/QueryTestBase

[zhengruifeng]

What changes were proposed in this pull request?

Followup to SPARK-55910 / SPARK-56560. Merge the helper methods from SparkPlanTest (in org.apache.spark.sql.execution) into QueryTest/QueryTestBase (in org.apache.spark.sql), and reduce SparkPlanTest to a thin deprecated alias for backward compatibility.

Moved into trait QueryTestBase (non-anyfun instance helpers — no test(...) dependency, so they don't need the AnyFunSuite mixin that QueryTest adds):

• checkAnswer(DataFrame, SparkPlan => SparkPlan, Seq[Row], Boolean)
• checkAnswer2(DataFrame, DataFrame, (SparkPlan, SparkPlan) => SparkPlan, Seq[Row], Boolean)
• doCheckAnswer(Seq[DataFrame], Seq[SparkPlan] => SparkPlan, Seq[Row], Boolean)
• checkThatPlansAgree(DataFrame, SparkPlan => SparkPlan, SparkPlan => SparkPlan, Boolean)

Moved into object QueryTest (static helpers):

• checkAnswer(DataFrame, SparkPlan => SparkPlan, SparkPlan => SparkPlan, Boolean, SQLContext)
• checkAnswer(Seq[DataFrame], Seq[SparkPlan] => SparkPlan, Seq[Row], Boolean, SQLContext)
• executePlan(SparkPlan, SQLContext)

SparkPlanTest becomes:

• @deprecated private[sql] trait SparkPlanTest extends QueryTest
• @deprecated private[sql] object SparkPlanTest { /* thin delegates to QueryTest */ }

Existing subclasses (SortSuite, ExchangeSuite, BroadcastExchangeSuite, InnerJoinSuite, OuterJoinSuite, ExistenceJoinSuite, SingleJoinSuite, TakeOrderedAndProjectSuite, ReuseExchangeAndSubquerySuite, BatchEvalPythonExecSuite, ExtractPythonUDFsSuite, BaseScriptTransformationSuite) and call sites of SparkPlanTest.{checkAnswer, executePlan} (in BaseScriptTransformationSuite, SingleJoinSuite, HiveScriptTransformationSuite) keep working unchanged via the deprecated aliases.

Also dropped the = NUM_VALUES default on the private ParquetVectorizedSuite.checkAnswer to avoid the Scala "multiple overloaded alternatives ... define default arguments" error against the new QueryTestBase.checkAnswer (both call sites already pass batchSize explicitly, so behavior is unchanged).

Why are the changes needed?

Consolidates the test-helper surface into QueryTest/QueryTestBase, matching the direction of SPARK-55910/SPARK-56560. New test suites can extend QueryTest directly instead of having to pick between QueryTest and SparkPlanTest.

Does this PR introduce any user-facing change?

No, test-only.

How was this patch tested?

Locally compiled sql/Test/compile and hive/Test/compile. Ran SortSuite (255 tests), ParquetVectorizedSuite (25 tests), and SingleJoinSuite (36 tests) — all pass. Relying on CI for full test run.

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[HyukjinKwon]

Merged to master.