count() to merge with filterNotNull and filterIsInstance + changed test for KT-14191 to use sum()

idea/testData/intentions/loopToCallChain/KT14191.kt.after

@@ -0,0 +1,9 @@
+// WITH_RUNTIME
+// INTENTION_TEXT: "Replace with 'filterNotNull().sum()'"
+// INTENTION_TEXT_2: "Replace with 'asSequence().filterNotNull().sum()'"
+fun f(list: List<Int?>): Int{
+    val r = list
+            .filterNotNull()
+            .sum()
+    return r
+}