JS IR: materialize Unit in lambdas

^KT-52010 fixed

js/js.translator/testData/box/expression/function/lambdaReturnValue.kt

@@ -0,0 +1,35 @@
+// EXPECTED_REACHABLE_NODES: 1285
+
+fun <T> rawReturnValue(fn: () -> T): Any {
+    return fn() as Any
+}
+
+fun unitFun() {}
+
+fun charFun(): Char = 'a'
+
+value class VC(val v: Int)
+
+fun vcFun(): VC = VC(1)
+
+
+
+fun box(): String {
+    if (rawReturnValue { unitFun() } != Unit) return "fail1.1"
+    if (rawReturnValue<Unit> { unitFun() } != Unit) return "fail1.2"
+    if (rawReturnValue<Any> { unitFun() } != Unit) return "fail1.3"
+
+    val boxedA: Any = 'a'
+
+    if (rawReturnValue { charFun() } != boxedA) return "fail2.1"
+    if (rawReturnValue<Char> { charFun() } != boxedA) return "fail2.2"
+    if (rawReturnValue<Any> { charFun() } != boxedA) return "fail2.3"
+
+    val boxed1: Any = VC(1)
+
+    if (rawReturnValue { vcFun() } != boxed1) return "fail3.1"
+    if (rawReturnValue<VC> { vcFun() } != boxed1) return "fail3.2"
+    if (rawReturnValue<Any> { vcFun() } != boxed1) return "fail3.3"
+
+    return "OK"
+}