Support new repeatable annotations in kotlin-reflect

- Unwrap Kotlin-repeatable annotations (with implicit container)
- Introduce `KAnnotatedElement.findAnnotations` to find instances of
  repeated annotations

 #KT-12794

libraries/stdlib/jvm/runtime/kotlin/jvm/internal/RepeatableContainer.java

@@ -0,0 +1,17 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package kotlin.jvm.internal;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.ANNOTATION_TYPE)
+// @SinceKotlin(version = "1.6")
+public @interface RepeatableContainer {
+}

libraries/tools/binary-compatibility-validator/reference-public-api/kotlin-reflect.txt

@@ -6,6 +6,10 @@ public final class kotlin/reflect/full/IllegalPropertyDelegateAccessException :
 	public fun <init> (Ljava/lang/IllegalAccessException;)V
 }
 
+public final class kotlin/reflect/full/KAnnotatedElements {
+	public static final fun findAnnotations (Lkotlin/reflect/KAnnotatedElement;Lkotlin/reflect/KClass;)Ljava/util/List;
+}
+
 public final class kotlin/reflect/full/KCallables {
 	public static final fun callSuspend (Lkotlin/reflect/KCallable;[Ljava/lang/Object;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 	public static final fun callSuspendBy (Lkotlin/reflect/KCallable;Ljava/util/Map;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;

libraries/tools/binary-compatibility-validator/reference-public-api/kotlin-stdlib-runtime-merged.txt

@@ -4037,6 +4037,9 @@ public class kotlin/jvm/internal/ReflectionFactory {
 	public fun typeParameter (Ljava/lang/Object;Ljava/lang/String;Lkotlin/reflect/KVariance;Z)Lkotlin/reflect/KTypeParameter;
 }
 
+public abstract interface annotation class kotlin/jvm/internal/RepeatableContainer : java/lang/annotation/Annotation {
+}
+
 public final class kotlin/jvm/internal/ShortCompanionObject {
 	public static final field INSTANCE Lkotlin/jvm/internal/ShortCompanionObject;
 	public static final field MAX_VALUE S