Fold initializer & if to elvis: add test, rename tests, simplify code

Enhancement for KT-27016

idea/testData/intentions/foldInitializerAndIfToElvis/IsSideTypeFake.kt

@@ -0,0 +1,21 @@
+// IS_APPLICABLE: false
+interface A {
+    fun a() {}
+}
+
+open class B : A {
+    fun b() {}
+}
+
+interface C : A {
+    fun c() {}
+}
+
+fun test() {
+    val b = B()
+    if (<caret>b !is C) {
+        return
+    }
+    b.b()
+    b.c()
+}