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/jvm8/defaults/allCompatibility/accessor.kt

@@ -21,7 +21,7 @@ interface Test {
         return {
             foo = "O"
             foo + bar()
-        } ()
+        }.let { it() }
     }
 }