Supported initialization with assignment instead of declaration

idea/testData/intentions/loopToCallChain/firstOrNull_assignmentInitialization.kt

@@ -0,0 +1,12 @@
+// WITH_RUNTIME
+fun foo(list: List<String>) {
+    var result: String? = ""
+
+    result = null
+    <caret>for (s in list) {
+        if (s.length > 0) {
+            result = s
+            break
+        }
+    }
+}

idea/testData/intentions/loopToCallChain/firstOrNull_assignmentInitialization.kt.after

@@ -0,0 +1,6 @@
+// WITH_RUNTIME
+fun foo(list: List<String>) {
+    var result: String? = ""
+
+    <caret>result = list.firstOrNull { it.length > 0 }
+}