[AutoSparkUT] Add GPU test coverage for TypedImperativeAggregateSuite (object aggregate buffer)

[wjxiz1992]

Coverage gap

Apache Spark 3.3.0 ships an 11-test TypedImperativeAggregateSuite under spark/sql/core/src/test/scala/org/apache/spark/sql/TypedImperativeAggregateSuite.scala that exercises DataFrame aggregation through the TypedImperativeAggregate object-buffer pathway:

• Aggregate with object aggregate buffer, no group by
• Non-nullable / nullable aggregator behavior
• Input row containing null
• With group by
• Empty inputs (with / without group by)
• TypedImperativeAggregate in Window function context

None of these behaviors are currently exercised against the RAPIDS GPU path in tests/src/test/spark330/scala/org/apache/spark/sql/rapids/suites/. This complements existing RapidsDataFrameAggregateSuite with coverage for the imperative/object-buffer path specifically.

Intended test scope

Add RapidsTypedImperativeAggregateSuite extends TypedImperativeAggregateSuite with RapidsSQLTestsTrait, register in RapidsTestSettings.

Expected outcome

All 11 tests pass on the GPU path (confirmed locally; see PR). No exclusions required.