Use CommentSaver instead of manual comment handling

idea/testData/intentions/ifNullToElvis/CommentInBlock.kt.after

@@ -1,4 +1,5 @@
 fun foo(p: List<String?>): Int {
-    val v = p[0] ?: <caret>return -1 // return -1 if null
+    val v = p[0] ?: // return -1 if null
+            <caret>return -1
     return v.length
 }

idea/testData/intentions/ifNullToElvis/Comments.kt.after

@@ -1,5 +1,5 @@
 fun foo(p: List<String?>): Int {
-    val v = p[0] ?: <caret>return -1 /* null */
+    val v = p[0] ?: /* null */<caret>return -1
     // now check if v is null
     // return -1
     return v.length

idea/testData/intentions/ifNullToElvis/Comments2.kt.after

@@ -1,7 +1,7 @@
 fun foo(p: List<String?>): Int {
-    val v = p[0] ?: return -1 // v is null
+    val v = p[0] ?: // v is null
             // we should do something with it
-            // let's return -1
+            return -1 // let's return -1
     // end of if
     return v.length
 }