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/extensionFromClass.kt

@@ -1,5 +1,5 @@
 class A {
-    fun result() = (A::foo)(this, "OK")
+    fun result() = (A::foo).let { it(this, "OK") }
 }
 
 fun A.foo(x: String) = x