Always consider container's experimentality in ExperimentalUsageChecker

This results in more diagnostics usually, but allows library authors to
avoid annotating everything in each experimental class with the marker
(only the class needs to be annotated now)

 #KT-22759

compiler/frontend/src/org/jetbrains/kotlin/resolve/checkers/ExperimentalUsageChecker.kt

@@ -142,9 +142,7 @@ class ExperimentalUsageChecker(project: Project) : CallChecker {
 
             val container = containingDeclaration
             if (container is ClassDescriptor && this !is ConstructorDescriptor) {
-                for (annotation in container.annotations) {
-                    result.addIfNotNull(annotation.annotationClass?.loadExperimentalityForMarkerAnnotation())
-                }
+                result.addAll(container.loadExperimentalities(moduleAnnotationsResolver))
             }
 
             for (moduleAnnotationClassId in moduleAnnotationsResolver.getAnnotationsOnContainingModule(this)) {