j2k: flatten test cases and testData directory structure

Move j2k/test/tests -> j2k/tests, j2k/test/testData -> j2k/testData

j2k/testData/multiFile/GetterAndSetterUsages/1.kt

@@ -0,0 +1,11 @@
+public class AAA {
+    public var x: Int = 42
+
+    public fun foo() {
+        x = x + 1
+    }
+
+    public fun bar(b: B) {
+        System.out.println(b.YY)
+    }
+}