Reflection: add KAnnotatedElement.findAnnotation

#KT-12250 Fixed

compiler/testData/codegen/box/reflection/annotations/findAnnotation.kt

@@ -0,0 +1,15 @@
+// IGNORE_BACKEND: JS
+// WITH_REFLECT
+
+import kotlin.reflect.findAnnotation
+
+annotation class Yes(val value: String)
+annotation class No(val value: String)
+
+@Yes("OK")
+@No("Fail")
+class Foo
+
+fun box(): String {
+    return Foo::class.findAnnotation<Yes>()?.value ?: "Fail: no annotation"
+}

compiler/testData/codegen/light-analysis/reflection/annotations/findAnnotation.txt

@@ -0,0 +1,19 @@
+public final class FindAnnotationKt {
+    public final static @org.jetbrains.annotations.NotNull method box(): java.lang.String
+}
+
+@Yes
+@No
+public final class Foo {
+    public method <init>(): void
+}
+
+@java.lang.annotation.Retention
+public annotation class No {
+    public abstract method value(): java.lang.String
+}
+
+@java.lang.annotation.Retention
+public annotation class Yes {
+    public abstract method value(): java.lang.String
+}