JS: prohibit is checks against native interfaces. Warn about casts to native interfaces. Fix #KT-14037, fix #KT-14038

js/js.translator/testData/box/native/castToNativeInterface.kt

@@ -0,0 +1,20 @@
+// FILE: castToNativeInterface.kt
+@native interface I {
+    fun foo(): String
+}
+
+@native class A(x: String) : I {
+    override fun foo(): String = noImpl
+}
+
+fun createObject(): Any = A("OK")
+
+fun box() = (createObject() as I).foo()
+
+// FILE: castToNativeInterface.js
+function A(x) {
+    this.x = x;
+}
+A.prototype.foo = function() {
+    return this.x;
+}