FIR2IR: cache functions and their parents properly

compiler/testData/codegen/box/functions/invoke/castFunctionToExtension.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 fun box(): String {
     val f = fun (s: String): String = s
     val g = f as String.() -> String

compiler/testData/codegen/box/functions/invoke/kt3450getAndInvoke.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 //KT-3450 get and invoke are not parsed in one expression
 
 public class A(val s: String) {