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/genericMember.kt

@@ -2,4 +2,4 @@ class A<T>(val t: T) {
     fun foo(): T = t
 }
 
-fun box() = (A<String>::foo)(A("OK"))
+fun box() = (A<String>::foo).let { it(A("OK")) }