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

idea/testData/quickfix/override/nothingToOverride/doNotLooseAnnotations.kt

@@ -0,0 +1,10 @@
+// "Change function signature to 'fun f(a: Int)'" "true"
+annotation class annon
+
+open class A {
+    open fun f(a: Int) {}
+}
+
+class B : A(){
+    annon <caret>override fun f(a: String) {}
+}