feat(JS/IR isInterfaceImpl perf): improve isInterfaceImpl performance by memoize an result.

libraries/stdlib/js-ir/src/kotlin/reflection_js-ir.kt

@@ -9,8 +9,8 @@ import kotlin.reflect.js.internal.*
 @PublishedApi
 internal fun <T : Annotation> KClass<*>.findAssociatedObject(annotationClass: KClass<T>): Any? {
     return if (this is KClassImpl<*> && annotationClass is KClassImpl<T>) {
-        val key = annotationClass.jClass.asDynamic().`$metadata$`?.associatedObjectKey?.unsafeCast<Int>() ?: return null
-        val map = this.jClass.asDynamic().`$metadata$`?.associatedObjects ?: return null
+        val key = annotationClass.jClass.asDynamic().unsafeCast<Ctor>().`$metadata$`?.associatedObjectKey?.unsafeCast<Int>() ?: return null
+        val map = jClass.asDynamic().unsafeCast<Ctor>().`$metadata$`?.associatedObjects ?: return null
         val factory = map[key] ?: return null
         return factory()
     } else {