Convert FoldInitializerAndIfToElvisIntention to inspection and decrease severity to INFO

#KT-19643 Fixed

idea/testData/inspectionsLocal/foldInitializerAndIfToElvis/IfNotNull.kt

@@ -0,0 +1,6 @@
+// PROBLEM: none
+fun foo(p: List<String?>): Int {
+    val v = p[0]
+    <caret>if (v != null) return -1
+    return 0
+}