Handle withIndex() on arrays and CharSequences in ForLoopsLowering.

compiler/testData/codegen/box/controlStructures/forInArrayWithIndex/forInArrayWithIndexNoIndexOrElementVar.kt

@@ -0,0 +1,15 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// KJS_WITH_FULL_RUNTIME
+// WITH_RUNTIME
+
+val arr = arrayOf("a", "b", "c", "d")
+
+fun box(): String {
+    var count = 0
+
+    for ((_, _) in arr.withIndex()) {
+        count++
+    }
+
+    return if (count == 4) "OK" else "fail: '$count'"
+}

compiler/testData/codegen/box/controlStructures/forInArrayWithIndex/forInArrayWithIndexNotDestructured.kt

@@ -0,0 +1,17 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// KJS_WITH_FULL_RUNTIME
+// WITH_RUNTIME
+
+val arr = arrayOf("a", "b", "c", "d")
+
+fun box(): String {
+    val s = StringBuilder()
+
+    for (iv in arr.withIndex()) {
+        val (i, x) = iv
+        s.append("$i:$x;")
+    }
+
+    val ss = s.toString()
+    return if (ss == "0:a;1:b;2:c;3:d;") "OK" else "fail: '$ss'"
+}