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

idea/testData/quickfix/createFromUsage/createVariable/property/thisInNestedClass2.kt

@@ -0,0 +1,10 @@
+// "Create property 'foo'" "true"
+// ERROR: Property must be initialized or be abstract
+
+class A<T>(val n: T) {
+    inner class B<U>(val m: U) {
+        fun test(): A<Int> {
+            return this@A.<caret>foo
+        }
+    }
+}