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/bytecodeText/capturedVarsOptimization/capturedValInLambdaInitializedOutside.kt

@@ -3,7 +3,7 @@ fun box(): String {
     x = "OK"
     {
         val y = x
-    }()
+    }.let { it() }
     return x
 }