Handle situation where KSerializer is absent from immediate supertypes

of the class used in @UseSerializers: Use methods to receive
full list of supertypes.

K1 supertypes() call returned all supertypes, while
IrClass.supertypes and FirClassSymbol.resolvedSuperTypes return only immediate ones.

This lead to a difference in behavior between K1 and K2, and regression
after plugin backend was rewritten from descriptors to IR.

#KT-55340 Fixed

plugins/kotlinx-serialization/kotlinx-serialization.backend/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/BaseIrGenerator.kt

@@ -82,10 +82,10 @@ abstract class BaseIrGenerator(private val currentClass: IrClass, final override
     }
 
     val additionalSerializersInScopeOfCurrentFile: Map<Pair<IrClassSymbol, Boolean>, IrClassSymbol> by lazy {
-        getClassListFromFileAnnotation(SerializationAnnotations.additionalSerializersFqName,)
+        getClassListFromFileAnnotation(SerializationAnnotations.additionalSerializersFqName)
             .associateBy(
                 { serializerSymbol ->
-                    val kotlinType = (serializerSymbol.owner.superTypes.find(IrType::isKSerializer) as? IrSimpleType)?.arguments?.firstOrNull()?.typeOrNull
+                    val kotlinType = getAllSubstitutedSupertypes(serializerSymbol.owner).find(IrType::isKSerializer)?.arguments?.firstOrNull()?.typeOrNull
                     val classSymbol = kotlinType?.classOrNull
                         ?: error("Argument for ${SerializationAnnotations.additionalSerializersFqName} does not implement KSerializer or does not provide serializer for concrete type")
                     classSymbol to kotlinType.isNullable()