feat: allow removing the default namespace index of an informer

[afalhambra-hivemq]

Adds a withoutNamespaceIndex option, on the @Informer annotation and both config builders. When set, the pool calls removeNamespaceIndex() on the informer before starting it.

Couple of things I'd like your opinion on:

• I made it part of InformerClassifier equality, unlike informerListLimit. The index can't be there for one event source and gone for another on a shared informer, so ones that disagree end up with separate informers, and the pool warns about it.
• Left it opt in instead of just always dropping the index, since that would change cache behavior for everyone in a minor release. Happy to make it unconditional if you'd rather.

There are unit tests plus WithoutNamespaceIndexIT, and a short docs section. Had to update the informer pool identity list in the docs too.

Unrelated, but I noticed it on the way: InformerEventSourceConfiguration.Builder.updateFrom doesn't copy comparableResourceVersions, so setting it on a dependent gets parsed and then quietly reset to the default. Didn't touch it here, will open a separate issue.

Fixes #3615

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[Copilot]

🟡 Changes recommended

Two moderate compatibility findings and one documentation nit remain unresolved.

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Pull request overview

Adds opt-in withoutNamespaceIndex support for informers, removing the default namespace index while preserving pooling correctness.

Changes:

• Adds annotation and builder configuration.
• Propagates the option through informer management and pooling.
• Adds identity handling, warnings, tests, and documentation.

File summaries

File	Summary
operator-framework/src/test/java/io/javaoperatorsdk/operator/baseapi/withoutnamespaceindex/WithoutNamespaceIndexTestReconciler.java	Configures the integration reconciler for the new option.
operator-framework/src/test/java/io/javaoperatorsdk/operator/baseapi/withoutnamespaceindex/WithoutNamespaceIndexIT.java	Adds end-to-end coverage.
operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/informer/pool/NonSharingInformerPoolTest.java	Tests non-sharing pool behavior.
operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/informer/pool/InformerClassifierTest.java	Tests classifier identity handling.
operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/informer/pool/DefaultInformerPoolTest.java	Tests duplicate-cache warning behavior.
operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/informer/pool/AbstractInformerPoolTest.java	Tests namespace-index removal.
operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerWrapperTest.java	Tests informer wrapper behavior.
operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerManagerConcurrentReleaseTest.java	Tests concurrent manager release behavior.
operator-framework-core/src/test/java/io/javaoperatorsdk/operator/api/config/InformerConfigurationTest.java	Tests configuration and builder support.
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/pool/InformerClassifier.java	Includes the option in informer identity. moderate (3 votes): retain the existing nine-argument constructor; nit (2 votes): correct the contradictory list-limit wording.
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/pool/DefaultInformerPool.java	Warns when differing settings create duplicate caches.
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/pool/AbstractInformerPool.java	Removes the namespace index before startup.
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/InformerManager.java	Propagates the setting to classifiers.
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/reconciler/Constants.java	Defines the default value.
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/informer/InformerEventSourceConfiguration.java	Adds event-source builder support.
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/informer/InformerConfiguration.java	Stores and exposes the option. moderate (3 votes): retain the previous protected constructor overload for compatibility.
operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/informer/Informer.java	Adds the annotation option.
docs/content/en/docs/documentation/eventing.md	Documents configuration and informer pooling behavior.

Review details

• Files reviewed: 18/18 changed files
• Comments generated: 3
• Review effort level: Lite

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[afalhambra-hivemq]

I'd rather not add compatibility overloads here. A constructor that quietly defaults the new field is how config silently goes missing. Leaving it open for @csviri to decide

[afalhambra-hivemq]

Same as previous one. And I think it would be worse in this case, since the classifier is the informer sharing key, so a caller could build one that silently disagrees about the index.