sum and sumBy supported

idea/testData/intentions/loopToCallChain/sum/sumByInts.kt

@@ -0,0 +1,10 @@
+// WITH_RUNTIME
+// INTENTION_TEXT: "Replace with 'sumBy{}'"
+// IS_APPLICABLE_2: false
+fun foo(list: List<String>): Int {
+    var l = 0
+    <caret>for (item in list) {
+        l += item.length
+    }
+    return l
+}