Fix temporary variable elimination in JS BE

Don't eliminate temporary variable when between its usage and its
definition there's assignment to a non-local variable.

Fix KT-17540

js/js.translator/testData/js-optimizer/temporary-variable/assignmentToOuterVar.optimized.js

@@ -0,0 +1,11 @@
+var value = "OK";
+
+function foo(newValue) {
+    var $tmp = value;
+    value = newValue;
+    return $tmp;
+}
+
+function box() {
+    return foo("fail");
+}