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

idea/testData/quickfix/nullables/unsafeInfixCall/unsafeInfixCall.kt

@@ -0,0 +1,4 @@
+// "Replace with safe (?.) call" "true"
+fun test(a : Int?) : Int? {
+    return a <caret>compareTo 6;
+}