[AA] Add KotlinPackageProviderMerger

- In parallel to Kotlin declaration provider merging, we need a proper
  merging strategy for package providers as well, because resolve
  extensions may define additional package providers.
- Additionally, other non-scope-based package providers may be added in
  the future, and the merger preserves these out of the box.

^KT-61791

analysis/analysis-api-standalone/src/org/jetbrains/kotlin/analysis/api/standalone/StandaloneAnalysisAPISessionBuilder.kt

@@ -144,6 +144,7 @@ public class StandaloneAnalysisAPISessionBuilder(
                 KotlinPackageProviderFactory::class.java,
                 KotlinStaticPackageProviderFactory(project, sourceKtFiles + declarationProviderFactory.getAdditionalCreatedKtFiles())
             )
+            registerService(KotlinPackageProviderMerger::class.java, KotlinStaticPackageProviderMerger(this))
 
             registerService(
                 FirSealedClassInheritorsProcessorFactory::class.java,