Big change in quickfix tests: no stupid test data format with "before" and "after" file prefixes

idea/testData/quickfix/createFromUsage/createFunction/get/createGetFromUsage1.kt

@@ -0,0 +1,6 @@
+// "Create function 'get'" "true"
+class Foo<T> {
+    fun x (y: Foo<Iterable<T>>) {
+        val z: Iterable<T> = y<caret>[""]
+    }
+}