j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/issues/kt-899.java

@@ -0,0 +1,7 @@
+//file
+class Test {
+    public void printNumbers(int number) {
+        for(int i = 2; i < Math.sqrt(number) + 1; i++)
+            System.out.println(i);
+    }
+}