add ultra-light classes/members that work without backend in simple cases

compiler/testData/asJava/ultraLightClasses/coroutines.kt

@@ -0,0 +1,19 @@
+/** should load cls */
+class Foo {
+  suspend fun doSomething(foo: Foo): Bar {}
+}
+
+/** should load cls */
+class Bar {
+  fun <T> async(block: suspend () -> T)
+}
+
+/** should load cls */
+interface Base {
+    suspend fun foo()
+}
+
+/** should load cls */
+class Derived: Base {
+    override suspend fun foo() { ... }
+}