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/innerConstructorFromExtension.kt

@@ -5,7 +5,7 @@ class A {
     }
 }
 
-fun A.foo() = (A::Inner)(this).o + (A::Inner)(this).k
+fun A.foo() = (A::Inner).let { it(this) }.o + (A::Inner).let { it(this) }.k
 
 fun box(): String {
     val result = A().foo()