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/jvmName/callableReference.kt

@@ -6,7 +6,7 @@
 fun foo() = "foo"
 
 fun box(): String {
-    val f = (::foo)()
+    val f = (::foo).let { it() }
     if (f != "foo") return "Fail: $f"
 
     return "OK"