Make several tests running on JS backend.

compiler/testData/codegen/box/casts/mutableCollections/reifiedIsWithMutable.kt

@@ -1,10 +1,5 @@
-// TODO: muted automatically, investigate should it be ran for JS or not
-// IGNORE_BACKEND: JS
-
 // WITH_RUNTIME
 
-import java.util.*
-
 class Itr : Iterator<String> by ArrayList<String>().iterator()
 class MItr : MutableIterator<String> by ArrayList<String>().iterator()
 class LItr : ListIterator<String> by ArrayList<String>().listIterator()
@@ -36,6 +31,8 @@ class MME : MutableMap.MutableEntry<String, String> {
 inline fun <reified T> reifiedIs(x: Any): Boolean = x is T
 inline fun <reified T> reifiedIsNot(x: Any): Boolean = x !is T
 
+fun assert(condition: Boolean, message: () -> String) { if (!condition) throw AssertionError(message())}
+
 fun box(): String {
     val itr = Itr() as Any
     val mitr = MItr()