JVM IR: Avoid direct invokes in callable reference tests

Due to the direct invoke optimization, most callable reference tests
were not generating callable references/lambdas.

compiler/testData/codegen/box/closures/localFunInInit.kt

@@ -3,7 +3,7 @@ class A {
     init {
         val flag = "OK"
         fun getFlag(): String = flag
-        result = { getFlag() } ()
+        result = { getFlag() }.let { it() }
     }
 }
 fun box(): String = A().result