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

js/js.translator/testData/box/dynamic/_common.kt

@@ -1,13 +1,10 @@
 package foo
 
-@native
-var bar: dynamic = noImpl
+external var bar: dynamic = noImpl
 
-@native
-var arr: dynamic = noImpl
+external var arr: dynamic = noImpl
 
-@native
-var baz: dynamic = noImpl
+external var baz: dynamic = noImpl
 
 object t {
     override fun toString() = "object t {}"

js/js.translator/testData/box/dynamic/is.kt

@@ -3,8 +3,7 @@ package foo
 
 class A
 
-@native
-class B
+external class B
 
 fun box(): String {
     val a: dynamic = A()