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/unit/kt4265.kt

@@ -1,13 +1,13 @@
-fun <T : Any, R> T.let(f: (T) -> R): R = f(this)
+fun <T : Any, R> T.myLet(f: (T) -> R): R = f(this)
 
 fun box(): String {
     val o: String? = null
 
     var state = 0
 
-    o?.let {
+    o?.myLet {
         state = 1
-    } ?: ({ state = 2 })()
+    } ?: { state = 2 }.let { it() }
 
     if (state != 2) return "Fail: $state"
     return "OK"

compiler/testData/codegen/box/unit/sillyThings.kt

@@ -30,11 +30,11 @@ fun box(): String {
     val tmp = Unit
     {
 
-    }()
+    }.let { it() }
 
     val tmp2 = {
 
-    }()
+    }.let { it() }
 
     val tmp3 = Blumbs()
     tmp3.t = Unit