[SPARK-55105][SS] Add Integration Test for Join Operator

[zifeif2]

What changes were proposed in this pull request?

Adding integration test for join operator, including V1, V2 and V3.
V1 and V2 join operator use multiple state stores with single column family, while V3 uses a single state store with multiple column families

Why are the changes needed?

Adding integration test for all operators to ensure repartition correctness

Does this PR introduce any user-facing change?

No

How was this patch tested?

Add added test

Was this patch authored or co-authored using generative AI tooling?

yes. Sonnet 4.5

[github-actions]

JIRA Issue Information

=== New Feature SPARK-55105 ===
Summary: Test repartition for Join
Assignee: None
Status: Open
Affected: ["4.1.1"]

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[zifeif2]

Changing this to abstract class instead of trait because here is the inheritance chain

  1. OfflineStateRepartitionIntegrationSuite (class) extends OfflineStateRepartitionIntegrationSuiteBase (trait)                                                                                                                         
  2. OfflineStateRepartitionIntegrationSuiteBase (trait) extends StateDataSourceTestBase (trait)                                                                                                                                         
  3. StateDataSourceTestBase (trait) extends StreamTest (trait)                                                                                                                                                                          
  4. StreamTest (trait) extends QueryTest (abstract class)                                                                                                                                                                               
  5. QueryTest (abstract class) extends PlanTest (trait)                                                                                                                                                                                 
  6. PlanTest (trait) extends SparkFunSuite (class) 

which means that there is a concrete class → trait → trait → abstract class → trait → class.
In Scala, traits cannot safely hide or defer concrete superclasses for concrete subclasses; the concrete superclass must be resolved at a class boundary. Making this an abstract class allows it to legally “anchor” the concrete superclass in the inheritance chain, ensuring correct class linearization and avoiding illegal inheritance errors during compilation