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

idea/testData/quickfix/createFromUsage/createFunction/set/setterForIncrement.kt

@@ -0,0 +1,9 @@
+// "Create function 'set'" "true"
+class A {
+    fun get(s: String): Int = 1
+}
+
+fun foo() {
+    var a = A()
+    a<caret>["1"]++
+}