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

idea/testData/quickfix/migration/lambdaSyntax/lambdaInsideLambda.kt

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