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/callableReference/function/constructorFromTopLevelNoArgs.kt

@@ -2,4 +2,4 @@ class A {
     var result = "OK"
 }
 
-fun box() = (::A)().result
+fun box() = (::A).let { it() }.result