[JS IR BE] lateinit support

* Functions with IrExpressionBody are lowered to IrBlockBody
* Implemented throwUninitializedPropertyAccessException function

libraries/stdlib/js/irRuntime/exceptions.kt

@@ -98,4 +98,8 @@ fun THROW_NPE() {
     throw NullPointerException()
 }
 
-fun error(s: String): Nothing = throw IllegalStateException(s, null)
+fun error(s: String): Nothing = throw IllegalStateException(s, null)
+
+@PublishedApi
+internal fun throwUninitializedPropertyAccessException(name: String): Nothing =
+    throw UninitializedPropertyAccessException("lateinit property $name has not been initialized")