JS backend: use special JsScope(JsDynamicScope) for names from dynamic calls instead of use containing scope to avoid the impact on local names.

js/js.translator/testData/dynamic/cases/nameClashing.kt

@@ -0,0 +1,26 @@
+package foo
+
+fun assertContains(expectedName: String, f: () -> Unit) {
+    val s = f.toString()
+    assertTrue(s.contains(expectedName), "\"$s\" dosn't contain \"$expectedName\"")
+}
+
+fun box(): String {
+    val d: dynamic = bar
+
+    val a = {
+        val somethingBefore = 1
+        d.somethingBefore
+    }
+
+    assertContains("var somethingBefore = 1;", a)
+
+    val b = {
+        d.somethingAfter
+        val somethingAfter = 1
+    }
+
+    assertContains("var somethingAfter = 1;", b)
+
+    return "OK"
+}