[VL][Iceberg] Register iceberg spark session extensions automatically

[infvg]

Gluten detects the Velox Iceberg component but does not register IcebergSparkSessionExtensions. Registered IcebergSparkSessionExtensions. Resolves #12693 (comment)

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[Copilot]

Pull request overview

Automatically registers component-provided Spark session extensions, including Iceberg’s extension for Velox, while preserving configured extensions.

Changes:

• Added component session-extension support and merging.
• Registered IcebergSparkSessionExtensions for Velox Iceberg.
• Added extension deduplication and Iceberg procedure parsing tests.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
gluten-ut/test/src/test/scala/org/apache/gluten/GlutenSessionExtensionsSuite.scala	Tests extension merging and deduplication.
gluten-iceberg/src/test/scala/org/apache/gluten/execution/IcebergSuite.scala	Verifies Iceberg procedures parse without manual configuration.
gluten-core/src/main/scala/org/apache/gluten/GlutenPlugin.scala	Merges component extensions into Spark configuration.
gluten-core/src/main/scala/org/apache/gluten/component/Component.scala	Adds the component extension API.
backends-velox/src-iceberg/main/scala/org/apache/gluten/component/VeloxIcebergComponent.scala	Supplies the Iceberg Spark session extension.

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[malinjawi]

Hi @infvg, we found an issue after this change when the Iceberg runtime is on the classpath. Tracking issue: #12912.

IcebergSparkSessionExtensions is now enabled for every Gluten session. Iceberg’s row-lineage rules then process non-Iceberg DataSource V2 tables, causing UPDATE and MERGE operations to fail with:

scala.MatchError: org.apache.spark.sql.connector.catalog.InMemoryRowLevelOperationTable

The extension can also unexpectedly wrap other configured SQL parsers.

Community CI passed because the Iceberg runtime was not on the gluten-ut test classpath, so the Iceberg component remained inactive during those tests.

The safest fix seems to be keeping the new component extension mechanism, but not registering the Iceberg extension globally. Iceberg applications and tests can configure it explicitly, and we can add the runtime to gluten-ut so mixed-format sessions are covered.

Does this approach make sense to you?

[jackylee-ch]

Sorry for the late review. For cloud products or internal platforms that provide standardized components, the Iceberg extension is often not enabled by default, even when Iceberg itself is available.
In that case, making this configurable and loading it only when needed may better fit real-world usage. @infvg Could we consider reverting the current change and leave this decision to users, especially since this functionality depends on a third-party component?

[infvg]

@jackylee-ch yep that's a good point, let's revert it #12913