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/abstractClassMember.kt

@@ -6,4 +6,4 @@ class B : A() {
     override fun foo() = "OK"
 }
 
-fun box(): String = (A::foo)(B())
+fun box(): String = (A::foo).let { it(B()) }