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

idea/testData/quickfix/migration/lambdaSyntax/labelInLiteralArgument.kt.after

@@ -0,0 +1,10 @@
+// "Migrate lambda syntax" "true"
+
+class A
+
+fun foo(a: Int.(String) -> A) {}
+
+val a = foo(fun Int.a(a: String): A {
+    A()
+    return A()
+})