JS: replace all usages of @native annotation with external modifier, in tests, stdlib, etc

js/js.translator/testData/box/propertyAccess/enumerable.kt

@@ -1,11 +1,9 @@
 // FILE: enumerable.kt
 package foo
 
-@native
-fun <T> _enumerate(o: T): T = noImpl
+external fun <T> _enumerate(o: T): T = noImpl
 
-@native
-fun <T> _findFirst(o: Any): T = noImpl
+external fun <T> _findFirst(o: Any): T = noImpl
 
 class Test() {
     val a: Int = 100

js/js.translator/testData/box/propertyAccess/nativePropertiesNameClashes.kt

@@ -3,8 +3,8 @@ package foo
 val PACKAGE = "kotlin.modules.JS_TESTS.foo"
 
 class A
-@native val Any.__proto__: String get() = noImpl
-@native val A.__proto__: String get() = noImpl
+external val Any.__proto__: String get() = noImpl
+external val A.__proto__: String get() = noImpl
 
 fun box(): String {
     val a = A()