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

compiler/testData/codegen/bytecodeListing/annotations/repeatable/kotlinAnnotation.txt

@@ -1,3 +1,4 @@
+@kotlin.jvm.internal.RepeatableContainer
 @java.lang.annotation.Retention(value=RUNTIME)
 @kotlin.Metadata
 public annotation class test/A$Container {

compiler/testData/codegen/bytecodeListing/annotations/repeatable/kotlinSpecificTargets.txt

@@ -1,4 +1,5 @@
 @kotlin.annotation.Target(allowedTargets=[FILE, TYPEALIAS])
+@kotlin.jvm.internal.RepeatableContainer
 @java.lang.annotation.Retention(value=RUNTIME)
 @java.lang.annotation.Target(value=[])
 @kotlin.Metadata

compiler/testData/codegen/bytecodeListing/annotations/repeatable/multipleRepeatableOrder.txt

@@ -1,3 +1,4 @@
+@kotlin.jvm.internal.RepeatableContainer
 @java.lang.annotation.Retention(value=RUNTIME)
 @kotlin.Metadata
 public annotation class test/A$Container {
@@ -16,6 +17,7 @@ public annotation class test/A {
     public inner class test/A$Container
 }
 
+@kotlin.jvm.internal.RepeatableContainer
 @java.lang.annotation.Retention(value=RUNTIME)
 @kotlin.Metadata
 public annotation class test/B$Container {
@@ -34,6 +36,7 @@ public annotation class test/B {
     public inner class test/B$Container
 }
 
+@kotlin.jvm.internal.RepeatableContainer
 @java.lang.annotation.Retention(value=RUNTIME)
 @kotlin.Metadata
 public annotation class test/C$Container {

compiler/testData/codegen/bytecodeListing/annotations/repeatable/retentionAndTarget.txt

@@ -1,4 +1,5 @@
 @kotlin.annotation.Retention(value=BINARY)
+@kotlin.jvm.internal.RepeatableContainer
 @java.lang.annotation.Retention(value=CLASS)
 @kotlin.Metadata
 public annotation class RetentionBinary$Container {
@@ -17,6 +18,7 @@ public annotation class RetentionBinary {
     public inner class RetentionBinary$Container
 }
 
+@kotlin.jvm.internal.RepeatableContainer
 @java.lang.annotation.Retention(value=RUNTIME)
 @kotlin.Metadata
 public annotation class RetentionRuntime$Container {
@@ -35,6 +37,7 @@ public annotation class RetentionRuntime {
 }
 
 @kotlin.annotation.Retention(value=SOURCE)
+@kotlin.jvm.internal.RepeatableContainer
 @java.lang.annotation.Retention(value=SOURCE)
 @kotlin.Metadata
 public annotation class RetentionSource$Container {
@@ -54,6 +57,7 @@ public annotation class RetentionSource {
 }
 
 @kotlin.annotation.Target(allowedTargets=[ANNOTATION_CLASS, TYPE])
+@kotlin.jvm.internal.RepeatableContainer
 @java.lang.annotation.Retention(value=RUNTIME)
 @java.lang.annotation.Target(value=[ANNOTATION_TYPE, TYPE_USE])
 @kotlin.Metadata
@@ -75,6 +79,7 @@ public annotation class TargetAnnotationClassAndTypeOnly {
 }
 
 @kotlin.annotation.Target(allowedTargets=[CLASS])
+@kotlin.jvm.internal.RepeatableContainer
 @java.lang.annotation.Retention(value=RUNTIME)
 @java.lang.annotation.Target(value=[TYPE])
 @kotlin.Metadata
@@ -96,6 +101,7 @@ public annotation class TargetClassOnly {
 }
 
 @kotlin.annotation.Target(allowedTargets=[])
+@kotlin.jvm.internal.RepeatableContainer
 @java.lang.annotation.Retention(value=RUNTIME)
 @java.lang.annotation.Target(value=[])
 @kotlin.Metadata