[Gen AI] Fix 11758: Ensure @Replaces beans are detected globally

[Jarvx]

Issue: #11758

Bug description

The bug occurs because replacement beans (@Replaces) are only discovered among the candidate collection being considered, not across the global registry. As a result, replacements declared elsewhere in the registry (e.g., a non-@Context replacement for a @Context bean) can be missed, and already-cached singleton instances for the replaced bean can remain in singleton caches, leading to nondeterministic behavior.

Solution / fix

The test defines an @Context-scoped bean (OriginalContextApi) and a @Singleton replacement (ReplacementSingletonApi) annotated with @Replaces(OriginalContextApi). It asserts that after starting the ApplicationContext, the original @Context bean is not instantiated and that injecting ReplacedApi yields the replacement. On the original code, the test fails because the original @Context bean is eagerly created, reproducing the reported issue where replacing a @Context bean with a non-@context bean still instantiates the original. This is aligned with the issue description. 2)

Patch effectiveness: The patch makes two key changes. In DefaultBeanContext, it scans all bean definitions for replacements and prunes any eager (@Context) beans from eagerInit if they are replaced, regardless of the replacement's scope. This ensures the original @context bean is not eagerly created when there is any replacement, even if the replacement is not @Context. In SingletonScope, it removes the fallback from findBeanRegistrationByExactDefinition to the type/qualifier-based cache, preventing returning a previously created instance of a different bean definition. This addresses the nondeterministic case where an original singleton could be returned because it matched by type/qualifier. Together, these changes fix both parts of the issue: preventing unwanted eager instantiation and ensuring correct bean selection by exact definition.

Steps to reproduce

./gradlew :test-suite-kotlin-ksp:test

[Jarvx]

I'll close this pr first because the CI fails.

[dstepanov]

For the core functionality always add tests for Java. (Not Kotlin like in this PR, nor Groovy). In this case the test should go to inject-java module.

[dstepanov]

I don't understand why do you need to scan all the classes. The method has candidates all the possible candidates for this injection.

[Jarvx]

This PR is improved by a new test script and a new patch. Hope you find it useful.