New J2K: add multi-file conversion tests from old j2k

nj2k/testData/multiFile/GetterAndSetterUsages/1.kt

@@ -0,0 +1,14 @@
+// ERROR: Unresolved reference: yy
+package test
+
+class AAA {
+    var x = 42
+
+    fun foo() {
+        x = x + 1
+    }
+
+    fun bar(b: B) {
+        println(b.yy)
+    }
+}