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"
+}