KT-16828: use _ when appropriate in destructure intention

idea/testData/intentions/iterationOverMap/DataClassLast.kt.after

@@ -3,7 +3,7 @@
 data class My(val first: String, val second: Int)
 
 fun foo(list: List<My>) {
-    for ((first, second) in list) {
+    for ((_, second) in list) {
         println(second)
     }
 }

idea/testData/intentions/iterationOverMap/DataClassNotAllPropertiesUsed.kt.after

@@ -2,7 +2,7 @@
 
 fun main(args: Array<String>) {
     val list = listOf(MyClass(1, 2, 3, 4))
-    for ((a, b, c) in list) {
+    for ((a, _, c) in list) {
         println("$a$c")
     }
 }

idea/testData/intentions/iterationOverMap/ValueOnly.kt.after

@@ -2,7 +2,7 @@
 
 fun main(args: Array<String>) {
     val map = hashMapOf(1 to 1)
-    for ((key, value) in map) {
+    for ((_, value) in map) {
         println(value)
     }
 }